1999 EX coupe
I need to get a high flow cat and Magnaflow is what I am going with. I just am not sure which one to get. There are so many similar but different ones on their website. Obviously it would need an opening for the O2 sensor and have to have 2" in/out (I think that's what size the piping is at least). Would this one work?

http://www.car-sound.com/catalog/universal/540.aspx

The 54054 seems like the best fit. If anyone has any experience with this, I would appreciate it.
I had just gotten a cheapo off of ebay and it doesn't fit right.

http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWN%3AIT

Are all Magnaflows hi flow?
Also, how do you know if the O2 sensor is good? I have su****ions as my gas mileage isn't that good (23.89 mpg) and I have done everything else suggested in the forums.

 

that could be a cause of bad gas mileage, have you done plugs,wires,cap,rotor, new fuel filter?