I wanna add a universal cat since im putting in new piping for my 98 ek 4dr right now it has stock header/cat and piping...i wanna put some aftermarket headers a new cat and 2.25 piping with a ws2 ...my question is which cat will sit better a magnaflow oval shape cat or magnaflow round shape cat

 

There was a high flow cat on ebay I was going to buy. It was a round shape which I think would be the best. I also have a WSII

 

cat shape probably doesn't matter most of the time,

just make sure it a good brand cat and has the correct piping size