Hmm, interesting, I am running PCll with full system; no cat, no o2 etc. All I did was take the o2 sensors and zip them to the bottom of the bike. Still plugged in just hanging basically from the bottom of the engine. Dont remember exactly where I tied em off to but it has worked fine for 35000 miles. 107 rear wheel hp on Mike Velascos dyno. Used a micron map for 92 octane gas that was on dynojet website. That was the best one we found for mix and power after a number of dyno runs. Mike said no problem hanging the o2 gizmos and never has been one.