After months of misfiring and horrible gas mileage I finally decided to address my p0420 and but a new cat. But I noticed for about the same price I can get a downpipe instead. I'm just confused on 2.5 or 3 inch. I emailed zzp and they said 2.5 would be perfect but I've read through a few forums that say otherwise. I have an 04 gp GTP completely stock. I plan to eventually make a cai and purchase a power log.
Also I plan installing the dp myself. It looks like a couple Bolts and a pipe is there anything that may complicate that? And will I need any other parts that don't come with it
