The SES light comes on usually when I'm cruising on the freeway. It has also come on after going WOT on the freeway and when I let off it will come on. Also my milage has really decresed lately, down to 11 mpg, all around town driving though. It's not the oxygen sensor, I replaced that. It's not the thermostat I replaced the 160 with a 180. I do have one spark plug wire that is a little burnt from my headers.(Where can I buy one moroso wire?) Now I suspect it is the hypertech chip which I have heard nothing good about.(I didn't put it in the previous owner did) Would it be a good idea to replace it with the stock chip or some other chip? Please help me!

 

TTT

 

If you have a bad wire, EMI noise can cause false triggering of code 45.
Also, if the MAF sees abnormally high Airflow, (removed screens) poorly designed CAI, it can cause a fuel enrichment at cruise triggering a code 45.
Is your vacuum line connected to the FPR, this again will enrich the mixture causing, a code 45.
Also a bad TPS, or a saturated charcoal canister.

Just a few things to look for.

Cheers

Richard