I have a Greddy SP2 with stock mid pipe and Y pipe. Just picked up a Nismo Mid pipe. The Nismo Mid pipe is 3” and the Greddy SP2 and factory Y pipe are both 2.5”’s but the connecting flanges on the Nismo and the Greddy are both the same size and the bolts match up. Will I have leakage if I bolt these together ?

 

No problem. Get a couple of 2.5 inch gaskets. You will have plenty of contact area for a good seal.