Cam profiles are designed pending certain applications, youll be completely changing how the exhaust flows and therefrore how the head and cams will breathe.
Kind of like shoving huge overlap cams in a V8 and then bitching the car wont idle like standard...
the engine is designed as one large system, that youre f**king with. It will drive, itll also make way less power than an RB25DE from the factory. There is a reason so many people have complained about driveability after doing this exact conversion...