Originally Posted by X-Rated
I done this, double non-fouler with the drilled out one for the 02 sensor. I still get the code PO420 which is just saying the 2 sensors are similar in readings, I just use the code reader & erase. The other thing you will get is a rich running smell from the tailpipe due to not having a "cat". Haven't gotten into the computer yet to see if I can recalibrate the fuel mixture to a leaner mix but I will let you know.
I run the OBX style header (shorty) with the down pipe, kept the "res" & running a Flowtech Raptor muffler. I also have the "long" style cold air intake system.
You really need to take a trip to a dyno, one with a MasterTech or SCT flash capabilities if you have an XCal. It will be well worth the cost due to your mods and conditions- you should get an increase in power and fuel economy.
I'm wondering why this didn't get put up in the stickied threads list. My apologies SYZ.