When you're talking about modern classic cars, it's not that unusual to run into models that were banned from being sold in America. Those bans could happen for several reasons. But, thanks to the 25-year rule, they end up being legal anyway after a certain point. When those cars do become legal to import over to America under the normal rules, it's not unusual for them to skyrocket in value. These once fairly affordable cars become worth an absolute fortune, especially to American collectors who want that forbidden fruit they couldn't have until now. Plenty Of Legendary Cars Have Ended Up Being Banned From Sale PorscheAmong those cars that have ended up being banned from sale, there are quite a few that are now considered to be legendary. The most famous of those is perhaps the Porsche 959. This car was the center of an infamous row between Microsoft co-founder Bill Gates and the US government, which ended up in the Show & Display clause being introduced. The Audi RS2 Avant was also banned from being sold in America, as well as the more legendary TVR models such as the Tuscan.There is one legendary car, however, that eclipses many of those legendary banned models in status. It's a JDM performance legend, and it's only recently become available to legally import under normal US legislation. The R34 Nissan Skyline GT-R Is A Japanese Performance Legend That Was Banned In The US Bring A TrailerThere aren't many Japanese performance cars that are more iconic than the R34 Nissan Skyline GT-R. That was no doubt helped by it becoming famous as the ride of choice for Paul Walker's character in the Fast & Furious franchise. It's also got one of the most celebrated engines made by any Japanese automaker. That's the RB26DETT, a 2.6-liter twin-turbocharged inline-6. It was officially rated at 276 hp from the factory, but that was only due to a gentleman's agreement that existed between Japanese manufacturers at the time. Most people believe that its actual output was as much as 312 hp. It Was Incredibly Technologically Advanced For Its Time Bring A TrailerOne of the big draws of the R34 Nissan Skyline GT-R was that, compared to everything else it competed with, it was incredibly advanced. This put it on trend with other Japanese cars of the time, several of which led the way in technological innovations. It has a sophisticated all-wheel drive system. It has a whole gamut of computer systems that were right at the cutting-edge of automotive technology for the time. This includes an electronic four-wheel steering system that improved handling at higher speeds.All that technology didn't mean sacrificing its pure driving appeal, though. The R34 Skyline GT-R was only ever available with a manual transmission. Its engine is also a fairly old-school turbo unit, with all the character that comes with it. That includes plenty of pops and bangs, should you decide to tune things that way. It Had A Variant That Was Almost Terrifyingly Powerful Via: NissanAs you'll no doubt have noticed from the table earlier, the R34 Skyline GT-R had a huge number of variants. Most of them were very similar in terms of power and performance. The only one that really stood out was the Nismo Z-tune. Built late in the R34 GT-R's production run and using used cars as the basis for the modifications (Nismo specified that the base cars had to have less than 18,500 miles on the clock, be in mint condition and have no previous accident history), these cars had a 2.8-liter version of the twin-turbocharged inline-6. This produced a phenomenal 493 hp and 398 lb-ft of torque, giving it a 0-62 time of 3.8 seconds and a top speed of over 203 mph. This made the R34 GT-R almost terrifyingly powerful, even with that sophisticated all-wheel drive system helping to keep things reined in. It Wasn't Built To Federal Motor Vehicle Safety Standards (FMVSS) Or EPA emissions regulations Bring A TrailerThe R34 Nissan Skyline GT-R had a lot of ingredients to be a sales success in the US. It also seemed to fit in with plenty of other sports cars that were perfectly legal to be sold stateside. So, how come it was banned? Well, it looks like Nissan actually didn't want to sell it over there. The R34 Skyline GT-R was simply never built to federal standards or EPA emissions regulations. That meant there was no way for it to be sold brand-new in America, unless certain parts of the car were fundamentally altered. R34 GT-Rs Are Now Legal To Import To America... And Worth An Absolute Fortune!Bring A TrailerFor a long time, the R34 Nissan Skyline GT-R was completely unreachable to American buyers. That's if you wanted to stick to following import laws, anyway. But almost every model year of the R34 GT-R is now legal to import to America. The only year that isn't is the final year of production (2002), and that will become legal in 2027.As you'd expect, this has caused values of the R34 GT-R to absolutely skyrocket. A base model R34 GT-R will cost you around $156,359. A V-Spec I will cost you around $222,550, while a V-Spec II will set you back around $151,304. Those are some seriously high prices, and they're only going to get higher as time goes on. Other Previously Banned Performance Cars That Are Now Worth A FortuneBring A TrailerThe R34 Nissan Skyline GT-R is one of the most famous 'banned' cars out there. But, as you'll have seen from the earlier examples we mentioned, it's far from the only one. It's also far from the only 'banned' JDM car to skyrocket in value in recent years. All the examples below are great JDM performance cars that are worth a fortune now, thanks in part to them being legal to import to America! R32 Nissan Skyline GT-R Bring A TrailerBack at the end of the '80s and the beginning of the '90s, the R32 Nissan Skyline GT-R was doing for the sports car market what the R34 did a decade later. Often considered as the best JDM car of all time, the R32 GT-R was nicknamed Godzilla for a reason. It was the first car to have the setup of the RB26DETT engine, manual transmission and sophisticated all-wheel drive system that would define the incredible performance of the '90s GT-Rs. It was also the first GT-R to have the modern, angular GT-R look that we all know and love today.If you want an R32 GT-R today, you'll be expecting to pay around $45,705 for a base model. That's relatively cheap compared to some other JDM legends. But, that's still out of the range of the average enthusiast. R33 Nissan Skyline GT-R Bring A TrailerIf we're including that R32 Nissan Skyline GT-R here, we have to talk about the R33 iteration as well. This was more of an small evolution of the R32 rather than a significantly new car. But, with how great the R32 is, it's not worth breaking what doesn't need fixing. Much like the Nismo Z-tune that was made for the R34 GT-R, the R33 also got its own 2.8-liter, madcap tuned-up variant. This is the Nismo 400R, and it has 400 hp and 347 lb-ft of torque.An R33 GT-R will cost you around $138,444 on the used market. That makes it another JDM legend whose values have skyrocketed into six figures. For some, though, that huge price is well worth it, as this car is a true performance legend that's only going to go up more in value. Nissan Silvia S15 Spec-R Wikimedia Commons: Guillaume VacheyThe Silvia S15 Spec-R was a more affordable performance car than the Skyline GT-R in Nissan's JDM model lineup. It only had a 2-liter turbocharged inline-4, and didn't produce any more than 250 hp. That still gave it decent performance for a compact sports coupe, though. It's also becoming increasingly valuable. One Spec-R with very low miles and the 6-speed manual transmission sold for $46,250 last year. Mitsubishi Lancer Evolution VI Tommi Makinen Edition The regular Mitsubishi Lancer Evolution VI was special enough. The Tommi Makinen Edition is even cooler! This car was created to commemorate Makinen's four World Rally Championship wins, and it's got significant upgrades from the standard Evo VI. It's such a step up, in fact, that it's sometimes referred to as an Evo 6.5. It's also one of the most desirable Evo models on the planet. Two examples recently sold for $55,555and $56,555, easily making them two of the most expensive Mitsubishis ever sold.Sources: Classic.com, Mitsubishi, Nissan