I am hoping for some help here. I live in the Atlanta-area and need to pass emissions. I have the APR Downpipe and tried the stage 1, O2 spacer trick to get it to pass, but it throws a CEL. Instead of spending $1300 on parts to go back to the OEM exhaust, I would like to replace the APR cat with a universal one (not high-flow) that will not throw a CEL. In order to do that I need to know more about the OEM catalytic converter. I am assuming it is a 3-way converter, but I need more details around the cell count, efficiency/load, dimensions and type (spun vs. other). Any help would be greatly appreciated. I figure a Magnaflow would work, but I don't know which one to get. The only thing I am pretty sure about it that it will need a 3-inch inlet and outlet.

 

Ok, I solved the problem with help from 034 Motorsports. Using their aluminum banjo-style spacer, I crammed the o2 sensor end with steel wool. Drove it for about 40 miles after clearing the CEL and it didn't come back on. Passed emissions with flying colors while in the 93 octane stage 1 tune. Now, for me, it seems like the ideal would be for APR to make a stock (non-testpipe) program for stage 2 and keep the testpipe programs for 91, 93 and 100 octane. Just in case there is any confusion, this is a 2010 Audi A4 Avant with the APR downpipe.