Besides the interference problems the JDM twin turbo engines are very tough to get them to work properly. The origional car comes with a special programed ECU. There is also a black box controler controling the sequencial turbos. The system was susposed to spool up the primary turbo very quickly. But i understand there was a flat spot on the transsition. When I got mine I tried several ways to make it all work and I could never get more than five pounds of boost. I bought a turbo from a 2002 WRX and have been happy ever sence. I think the JDM twin turbo engines are over priced. They do have better heads and the cams have a higher lift and should produce more HP.
Don