I'm in the middle of replacing the Y-Pipe on my D2 and ran into some issues with leaks. I bought an aftermarket one on ebay, comes in two pieces with the mate between the two halves done with a clamp. I went this route because I thought it might actually give me a slight bit of adjustment if needed to fit it.
Anyway, got everything installed and it leaks at all three joints, but no check engine lights at least. Best I can tell, the mating flanges between the manifold and the y-pipe are not parallel, so when you tighten the three manifold bolts (on both sides I believe, but definitely the passenger side), the inner most part is tight, but there is a gap at the outer most side, hopefully that makes sense. I stupidly broke a stud thinking that I could tighten the outer bolt some more to close the gap even though I should have known better. Anyway, since I had to remove the RH manifold to take care of that. my thought is to mate the LH side, then mate the loose RH manifold to the y-pipe to get a good seal at that joint and then mate the manifold to the head. Seems logical but I'm just curious what others have done to get the seals tight.
The rear seal at the muffler is also leaking, I'm not sure what to do there yet, but I think I do have some room to play there since I can move the muffler around some.
Anyway, got everything installed and it leaks at all three joints, but no check engine lights at least. Best I can tell, the mating flanges between the manifold and the y-pipe are not parallel, so when you tighten the three manifold bolts (on both sides I believe, but definitely the passenger side), the inner most part is tight, but there is a gap at the outer most side, hopefully that makes sense. I stupidly broke a stud thinking that I could tighten the outer bolt some more to close the gap even though I should have known better. Anyway, since I had to remove the RH manifold to take care of that. my thought is to mate the LH side, then mate the loose RH manifold to the y-pipe to get a good seal at that joint and then mate the manifold to the head. Seems logical but I'm just curious what others have done to get the seals tight.
The rear seal at the muffler is also leaking, I'm not sure what to do there yet, but I think I do have some room to play there since I can move the muffler around some.