Quote Originally Posted by farmtruc View Post
Acutually, insufficient switching is kind of common when headers are installed. I see this all the time.

Here's what I don't get, header companies sell you a set of headers, ask if you want the ORY or cats. If you pay extra and get the cats, they flow to well, or the headers disrupted the o2 readings, that you have have to get the pcm tuned anyway to delete the cats and o2's.
I see this a lot with the camaros and vettes, especially the vettes.
Not sure exactly why, but when headers are installed, the pcm doesn't like the tight tolerance the o2 must obey. Those codes are usually thrown during idle and easy driving, give it a little gas and the o2's respond correctly.
I've requested from hptuners, to give me tables that allow adjustment of the high and low values, but nothing, it's only been a couple years now, lol.
You can turn the ses light off, but keep the code enabled, that's one solution. Or, like it was mentioned, swap the stock o2s with others that respond better.
Or if they're bad...

good luck,
allen
Sounds like it's because the thin wall long tubes allow the exhaust gasses to "excessively" cool before reaching the catalyst that requires high EGT to work properly....and the post cat O2 knows it. Under load the thin wall headers heat up faster than the thick (already hot) cast manifolds and the O2's repsond.