So I have 1000cc gsxr throttle bodies sitting in my room. I was going to do all motor but decided to give itb turbo a shot. The only question I have is: Are 42mm throttle bodies too small for itb turbo? Or should I go bigger (busa)? I am not looking for lots of whp. My goal is 275-300 whp. I found a thread a while back that said 42mm itb should outflow 68-70mm single throttle body. How true it is...I do not know that is why I'm asking. So any input on the sizing would be appreciated.

 

In order to use ITBs, you must have a central plenum like the Jenvey setups. for 300whp, this will be a waste of time as the stock manifold can do that without blinking.

 

The plenum isn't an issue. But I guess all the tuning etc that goes along with the itb's wouldn't be worth it for 300 whp since you can get that on a stock b18c on a good tune. Thanks for the answer.