yeah I have a 95 Firebird and it has only one code on the pcm which is the EGR code and I was wondering if performance or gas mileage will suffer any due to this?

 

Depends on what's going on. Is it a bad solenoid or a bad valve? If your EGR is bad, then yes you could be losing some performance/gas mileage.

 

Is the code a 27 or 32?

 

the valve is stuck closed and needs replacing. Will this effect my performance/gas mileage?

 

nope.

edit: yup

 

If you get detonation from the lack of EGR, then yes, you will have a performance loss from spark retard.

 

would detonation be caused from the cylinders being extra hot from lack of egr flow?

and also, does the computer do anything to the fuel injection/timing to give you a power loss because the code is in memory? excluding the knock sensor.