Welded a 2.5" high flow cat on the neon. The bolts shook loose holding the element in place on the old one and the damn thing kept rattling like crazy.
Anyways, the downpipe is 2.5" and behind the cat the pipe is 2.25" Not sure if this is a well known solution but this is what I did: Cut slits down the 2.5" pipe and hammered it around the 2.25" pipe, then welded up the seams. Works good!
Pipe funnel
