Check Engine light?
 

hey guys , i put on an off road h-pipe and since then the check engine light has been appearing on my dash , i have an 89 gt with about 150,000 miles on it. about 2000 miles ago i gave it a complete tune up , cap rotor , wires plugs and timing. i didnt use the best quality parts when i tuned her up. why do you think the engine light is coming on? any help is aprecitated.

Probably bad oxygen sensors. Is it on all the time?

Check and see what the codes are.

02 sensor, replace them, or take them out and clean them, but replace if you can, afterwards reset the computer, or else the computer wont find the fix.

Resting Computer
 

Thanks for the replies man, i was just wondering how i can go about resting the computer, ive never done it before and i was wondering if you could break it down for me , by the way the light isnt on all the time, it comes on periodicly , like on for a couple of seconds then off. thank guys for helpin me out.

Resting the computer?
 

???

If you mean resetting the computer, you should pull the codes first. The easiest way to reset the ECM is to disconnect the negative battery cable, and while it's disconnected, turn on the headlight switch for 15 seconds. This will make sure that any/all capacitors are discharged. Then reconnect the battery cable.

Take care,
-Chris