My SES light comes on and stays on for a few days after going 110-120mph. Had it scan and says #4 has misfire. Car drives great and gets awesome mpg. Whats up with this? Its a 99 firebird.

 

You probably had a misfire going that fast which set the SES light. If the scan says #4 misfire, you know where to look now. Shouldn't be too hard to pinpoint the problem (plug, wire, etc).

The light may go away after a while...but keep that #4 misfire in mind.

 

did you bounce off the rev limiter at all?

 

Mine used to come on after going 70 MPH... Replaced the 6 / 3 Coil pack... drives awsome... I suggest replacing the coil pack first