Originally Posted by Deuce Cam
4. This is complete guess but I'd imagine the ecu and knock control on the EVO is much more tuner friendly.
5. Mivec on the intake and exhaust cams.
The tuner friendly is more of an engine deal than a purely software/hardware ECU type deal. The 4G63 is much easier to tune because you can simply add fuel, advance timing, and add boost and make, in the words of Big Al, "Big Evo Power Bro!". Subarus are much more difficult to tune.
Also the MIVEC is only on Evo 9s and is fairly useless past 500hp. I know this because I have a buddy whos Evo 9 MR is currently at Buschur Racing in Ohio getting a Built 2L engine, PT6262 (although he has a HTA86 on order), complete 1000hp fuel system, advanced ignition system, Shepherd Stg 3 trans and transfer case, and drag racing coilover setup. He should be turning about 700hp on 93 pump. He is running a 280 cam and they can't advance it very far and barely makes a difference in spool or power. Some people even disable it.