Do you know the diameter of Stillen's Y-pipe?
 

Hi, I wonder whether you know the diameter of Stillen's Y-pipe for their Gen II exhaust. I have seen some people said 2 1/4" and as well as 2 1/2". Which one is correct? I am considering in putting flex couplings in the beginnng of the Y-pipe near the same location as factory Y-pipe to minimize flex coming from the engine. Has anyone done this to the Stillen exhaust? Do you think it is needed?

according to the stillen sales ppl , it is 2.5" to 3"
but i guess you can always measure the inner diameter?

especially when you want to do some custom work with it