Re: EGR valve code when all parts are new.
I had an 86 Firebird but only the 5.0 engine and it would throw a check engine light (not sure of code) but I remember everything pointing to the EGR valve. They also replaced everything around there and always came back after awhile I finally found there was a 1/8 plastic vac line on the back of the carb that went to I believe the MAP sensor on the firewall. It had rubber hose fittings on each end. Anyway, it would plug up the sensor with oil because of the 1/8" tube and then set a code. I finally just installed 1/4" tubing from the carb to the sensor and never had another issue. I don't remember mine being temp related but might be worth a look at. It's always hot in AZ.
69 Z/28. 302DZ, Autogear M22, Red w/black stripes.
69 Camaro, ZZ4, 700R4, 8.5 3:42 posi, X11
70 Nova SS 396, 4sp, 3:55 12 bolt