Ive got a 91 Formula and Im having problems already bolting it up. To make a long story short I ordered a y-pipe WITH cats from Summit Racing. (Those guys are great...pretty good tech support) I ordered Catco cats with the y-pipe
(part # cto-4153)...I got the package today....the box was ripped and beat. I opened the package and I have a feeling parts are missing. Anyway.. Ive got three pipes...1 pipe for each side of the manifold and the two cats. at the VERY end of the y-pipe is big big metal circle (its welded on there). I had a picture scanned so you guys can see what Im talking about but I cant upload it (dont ask why). Hopefully ill be able to scan it again tomarrow. I cant figure out for the life of me how I'll be able to bolt this up to my new exhaust...I went with borla...I know I know..some of you guys hate borla some of you guys love borla...
I did call summit and they said im only missing 2 exhaust flanges which they said they credit me for. They couldnt tell me how to "fit" the "end" of the y-pipe to the rest of the exhaust system. Hopefully you guys will be able to help me. This weekend im gonna install everything...wish me luck!!!!! Later

 

If I remember right, my stock exhaust had a metal donut looking end on the muffler side of the Y pipe. The pipe going to the muffler was flared and it went together with a clamp (which if you tighten too much will eat into the pipe.) You could try cutting the "donut" off and using a band clamp to put the two pieces together, good luck getting it not to leak. Or you could get it welded.

 

heres a picture of my dilemma...(hopefully..it will upload without problems)