I've got a Catco 9118 and and Hooker 2055 Headers. I'm trying to get the Y-Pipe to go into the cat, but it's a very tight fit. It's actually too tight to just slip into the cat. How do I fix this? I would like to complete my exhaust as soon as possible, because I also have to put the Flowmaster cat-back on too.

 

You could rent(for free) a tail pipe expander from an auto parts store to expand the inlet of your cat, but those might not be up to the task--even though that's what they're for.

Better to just take your cat to a muffler shop and have them expand the inlet on their expander. But make sure they don't get carried away(those machines do it so easily), because if they do go overboard, you'll have a difficult time securing your connection with a clamp.

 

info: When I installed SLP Headers, the connection between the Y-pipe and the Catco 9118 cat was made with a short Slip Fit connector pipe. In your case 2055 header who knows what they make for the fit??