Looking for some advise here. I just bought a downpipe and high flow cat from IE, for my a4. I don't have a stage 2 tune or any ecu tune for that matter. What I do have is the nuspeed power module and a O2 spacer for the O2 sensor to prevent a CEL. Is it possible to install the downpipe with high flow cat without a stage 2 tune, and without causing any major issues? I live in Ohio and we are required to get E-checks. Any help would be greatly appreciated. Thank you.