Alright before you go and tell me to SEARCH i have done it many times and no one yet can answer my guestion or problem. Heres my situation I bought a Y pipe from Warpspeed and it didnt fit perfectly up into my car, so I carved out one of the holes and we got it to fit. Now I see with the gaskets that they give you (metal circle ones) its causes leaks there. So I think I need to put new gaskets in there. Also at the end of the Y pipe where it connects to the cat its leaking there too because I have an original cat. So I want to replace it with a catco hi flow cat. The new Cat should fit better and it shouldnt leak. But now with the rest of my exhaust is what I have a problem with. Laws in Maine just passed making it almost impossible to pass a car with an aftermarket exhaust. So that puts the greddy catback of the list. Do you guys think I should put the Warpspeed b pipe in either 2.5 or 2.25 diameter size. I just need a solution thats going to fit and not going to leak. Here's my logic the Warpspeed y pipe is 2.5 in diameter, the Catco cat is also 2.5 diameter so do I need a b pipe with 2.5 diameter or can I go 2.25 and get a magnaflow muffler. I need some help on this one guys cause it stumps me. If i get 2.5 for a b pipe i cant get a magnaflow muffler. I just need some help on advice please and asap.
Anyhelp is very much appreciated....

 

I'm only going to address your first question/problem about leaking around the metal circle gaskets, perhaps someone else in the collective can answer your other questions. Try this... Go to your kitchen and get out the roll of aluminum foil. Tear off a sheet 12" long or so. Cut it into 1/2" - 1" wide strips. Wind the strips evenly around the metal gasket. Don't go nuts on the thickness but adding up to about .050" should be okay if it isn't wound real tight. Now, as you fetch the pipe up to the manifold, the gasket may slide out of that nice circular groove so go back to the kitchen and get out the hot glue gun and carefully center the gasket, then glue it (just enough to tack it well). When you torque the Y-pipe to the manifold, the soft aluminum foil should squish to fill the place that was allowing the leak.