so im going to use a header with a 2.5 collector and maybe use an omni test. What im trying to figure out is if I would the test pipe fit my exhaust system 2.25 piping because the test pipe should fit a 60mm exhuast system. And if it wouldnt would i need to get a oem flange or gasket from inline4???? Also im going to pay around 300 dollars for the install because the guy at the muffler shop said he would help install the header and exhaust in my sol. I would do the install myself but then one of my header bolts are fucked up so I took it to a muffler shop to see if they would drill and re thread it. Plus i need to find a bolt somewhere which should be cheap i hope.