Will the Cayenne Turbo throttle body fit into the stock Y-pipe of the 996 turbo and the 70mm RSS Plenum? if yes any power gains expected by using the bigger cayenne turbo throttle body with the stock Y-Pipe and RSS 70mm plenum?

 

bump! Interested myself.

 

I think CTT TB is around 82mm. In your case if you map with 70mm IPD:
1. I do not think that it would fit. Size is way diff.
2. If it fits, you wil have the step edge at the transition (82mm step to 70mm.). It would not benefit good flow.
Look for 997T,997 TB (75mm) and match with 75mmIPD. You will have both increase in size and smooth flow. (oe tb is 68mm.)

 

I think many here have done it, but it does require changing all your intake piping, if you haven't already. I think Dr Jitsu and Todd (vividracingtx) have one...

 

There's a thread on the vivid and IPD intakes that covers a great deal of this. It would be worth looking at both of those closely. I think Dan even threw a set of calipers on one of the TBs to better show the inside diameter. Just be sure to read the threads completely since some of the ifo kind of goes back and forth before sizes are finally figured out

 

bolt pattern of the flange is different so they wont fit.