Do you need to build the motor? Depends on the tune and how aggressive it is. You can get the GT30R and run a conservative tune (to be on the safe side) on your motor and easily get "mid to high 300whp"... depending on the dyno. How much stress can the motor take? Some say not a lot, some say a lot. Im one of those that believe that with a good tune, the EJ25 can take some beatings. There are some people that are running GT35R setups with 500whp on the stock block with out any problems. Then today I just saw Ultimate-Racings new turbo kit on the stock block making 450whp on 93 octane. Hope this helps.mk112288 said:I am currently debating whether or not to do a GT30R. If I am looking for mid to high 300 awhp, do I need to build the motor? How much stress can the stock block take?