I went with a napa gold because I couldn't beat the price. ( was like $18 but ended up free) I got it through a shop my buddy who's now in tech school with the dyno works at and they never sent the paperwork with the filter for the wholesale acct.

 

Just a note....when you dyno your car do not settle for the sensor up your tail pipe (assuming you have cats) also the sensor cannot be just up your pipe. It should be at a 90° to the exhaust flow. The sensor should be before your cats

James