Hey guys.. what I am trying to do is basically to have an aftermarket Y-pipe with a 3" outlet mated to a 3" B-pipe that goes straight through into a 3" muffler piping.

My question is.. what is the stock muffler piping? 2.5"? If it is 3", then I simply will give up on buying a full catback exhaust and just replace the Y-pipe and B-pipe.