please delete

If ya ever tried to take the stock turbo inlet pipe out without removing the intake manifold, you would find that it fits in there pretty well:). I don't think there can be a significant change in diameter from stock if you keep it under the intake manifold.

Hippy, I moved it to the 2.5 forum, my mistake. Perrin fits a larger ID 3" pipe that narrows to 2", so at least that much bigger works.

Yeh, the stock inlet pipe is actually bigger on the ends then in the middle also(I dunno about 3"), and the middle isn't cylindrical. It's more odd-shaped so it can fit under the intake manifold. That would be why it's hard to remove the stock inlet pipe without either taking the intake manifold off or cutting off the end closest to the turbo.