My car started to run rough and check engine.

I got the code checked it was the thermostat that I have in it is not letting the engine temp up to 195 like it is suppose to with the normal thermostat, so just get the front end checked to see if it is out of line, correct?

First I want to add it is supercharged.
We put a 3" downpipe on our Grand Prix now the check engine light is on and it is shifting really hard. It has a lot more power now and better gas mileage.
We also had to make the wires longer for the o2 sensor so that it would fit.
Can the upgraded exhaust be causing our problems? Is it the o2 sensor? Can we reset the computer or is there something we need to do to the computer?

I tried to email this question earlier and it didn't work, however I did get confirmation that my dontation was accepted. So I'm sending this as a free questions. So I'm sending it again. The service engine soon light came on--what does that mean and what does it cost to fix? I mixed ethanol gas with regular unleaded--could that be a factor. I get excellent gas mileage and my cars runs great. I get my oil changed every 3,000 miles and the new oil change has only 1,000 miles on it. My mpg are 25 in town and 31 hwy.

Hi, I was driving like normal today and all of the sudden, my service engine soon light comes on. I mean, it's not driving any differently, nor is it sounding any different. Any ideas?

Check engine light on, codes says 02 sensor bank 1 and 2. Replaced sensors light still on, auto tech reset check engine light, now light out but computer and sensor not talking, reading not tested heater lead not on