Originally Posted by
syfi
If the pipes are 2-1/4" up to the res, then should I be using a 2-1/2" X-pipe to slide over, or 2-1/4" X-pipe and butt weld it?
2.25" X, and neither option.
Most exhaust shops have pipe "spreaders" that can flare the ends of a pips so they fit snugly over each other. Do that, and secure the pipes with a clamp. Butt-welding can create turbulence in the pipe, if the welder isn't very skilled.