Just found a link for OBD-1 Diagnostic Trouble Codes (http://www.gmtuners.com/OBD1_DTC.htm)

so 21= Throttle Position Sensor (Signal High)

32 = EGR System Failure

what are you suggestions to fix them?

Go after the TPS problem first, a problem with the TPS can affect the monitoring of the egr system since at no time should the egr be in operation during full throttle or idle conditions. Use a digital multimeter and check the power and ground supply to the tps. The voltage should be in the neighborhood (+/- half a volt) of 5 volts. The tps is a low load item so doing a continuity check on the ground circuit should be sufficient. If both those circuits check out ok, replace the tps. Good luck:D

I would put a steel plate with a gasket underneath the EGR,leave vac line in place.
this wont cause SES light, and gets you a bit more power cause it wont be choking on the burnt gasses any more.

Do you have a picture of the plate and exactly where to put it?

Unbolt the EGR valve from the center of the intake. Put the thing on a piece of 1/16" or thicker sheet metal,trace the shape and bolt location on the metal, cut it out and drill the bolt holes.
Place gasket,plate and EGR on intake and bolt it down again.

Yeah but you still have exhaust gasses and soot going up under the intake heating it up. Better bet is to get j-code intake gaskets to block off the exhaust ports and an unrestricted intake...

http://www.dieselservices.com/html/gm_diesel/6_2_Litre_Diesel/gm-diesel-exhaust/intake_blockoff_plug_6265_p20.cfm



This is what I have.