Had my xj in storage for awhile now, pulled it out and started trying to fix some stuff with the exhaust specifically rattling, crawled under and boom a huge hole is rusted out. So I'm leaning towards a banks monster exhaust 2.5in. BUT I cant seem to find a specific answer to my question.... In regards to the exhaust being 2.5, could I use a thunderbolt cat at 2.25? and keep the front pipe at 2.25 as well? I'm sure its an easy answer but Im just not finding it

 

Unless you have a stroker, 2.25" is the ideal size, so sections of the system being 2.25" is just fine.

 

Keep it stock all you will see with an increased size is decreased ground clearance and more places to rattle against the frame.