Instead of having a custom Y-pipe made, is it easier and/or cheaper to convert the manifolds to the later 1.5" pipe size so that I can buy off the shelf pipe? Or is this too expensive or causes other problems such as fuel injection.

 

I changed out the Y on my 94, mind you its the narrower manifold, but the walker Y pipe is easily 2+ inches and it mated just fine. It's not a smooth bend pipe so there is internal resistance to air flow and the rest of the walker exhaust system including the CAT is 2.5"
Edit- It just occurred to me that if you wanted you could cut the mating ends off the existing pipe and weld it to the new pipe so an off the shelf would fit if you wanted to save the expense of buying new manifolds.

 

I doubt the PCM actually does too much about something like a change in exhaust sizing but it might. Whether it would cause a problem in engine function, I really doubt it.

It would detune the engine though by a few HP but if you could stomach that it's probably ok. IIRC the larger sized exhaust is big all the way to the muffler inlet, at least that's what the catalogs say.

Here's the 92 V6 muffler specs courtesy RA:


Here's the 94 muffler specs:


You might also be able to fit a reducer in there between the new Y and the existing front pipe so that would eliminate the change all the way back to and including the muffler.

Steve

 

Since you'd have to change all the way back to the muffler, including the muffler .... I'd opt for a custom Y pipe personally.

You could get the new Y pipe mandrel bent for that matter.

RwP