4G63 without a doubt. Yeah, there are all sorts of other 4 bangers, but none have the reputation of the 4G63. John Shepard, AMS, APR, and countless other people running the crap out of these little 2.0 engines with insane power, let alone for such a small engine...I'm worried that the Evo X wont have the same potential since it will be so vastly different.... DI, all aluminum, more MIVEC...yeah it'll be badass, but how far will we really be able to mod it and get crazy insane numbers again? I only hope the new turbo Lancer replacement is actually powered by 4G63...Mitsubishi knows the importance of the engine:

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Lancer Evolution 4G63 final model Special Contents