my catalytic converter recently started rattling on my 04 n/a mini. and i was wondering if anyone here has tried using a high flow cat before? if it would lose power? be too loud? or even smell?

If you live in a non-emissions area, I'd just purchase a high flow cat-less down pipe and delete the cats altogether.

depending on the flow of the cat and the rest of your exhasut you will thow a CEL for the cat being below efficency, the fix is a O2 spacer for the rear oxygen sensor.

happend to me on my R53 its 2.5" all the way from the collector allt the way out and it didnt like it so i put a spacer in and it was happy.

Suggestion...
Buy a used OEM header...they seem to sell for $150...comes with a cat in most cases...

Yea thats a good idea too. they are also both the same for R50 and R53 so dont limit your self to just looking at R50 sales.......... and probably the R52 but not sure

I believe there is an oem header for sale on the forum now for $150, no ones bit on it yet last I checked. Probably worth almost that in scrap.

Am I confused or doesn't the car have two cats? The one that was rattling didn't seem to be attached to the headers.

I think I might just go with a magnaflow high flow cat.

Also do you guys know if the back pressure lost through a high flow cat would make my car lose power? It's an 04 non s

Race cats are very loud, not sure if a high flow is considered a race car though.