My understanding is yes, an exhaust leak can cause a problem for the emissions system. It throws off the monitors examining the exhaust flow. I would imagine it would depend on how much of a leak you have. But apparently the tolerances are very tight, and any variation from "standard" would throw a code.

 

My leak though is definitely after the collectors. I looked at them this morning and saw they're tightly shut, so this means it's leaking from between the x pipe and overaxles.. which is after the cats. Would that have an effect on the sensors reading?

This morning I swapped the two sensors in the cats, so if p0430 comes up again then it's the cat or the leak.... or possibly the wires from the extension are faulty?? OH while I was underneath today, I started to bang around my fist in search of this gurgling-popping sounding noise that I only hear for 10 minutes after my car first starts (usually backing out of my flat driveway or slow rolling down the block). Its sounded like it was coming from INSIDE the left cat. What the heck could this be?? Is it defective?

This is so frustrating. I've had my headers and mid pipe for a year now. Didn't have p0430 coming up as often as I have in the last 4 months. Meanwhile I haven't seen p0420 once. Calling up BAMA for help this week, maybe they can write me a tune that allows for more oxygen flow through the cats so the code doesn't pop up