check engine light

so i got an 87 turbo bird and the check engine light keeps coming on. i have recently replaced the head gasket. all the fluid in it are at the right level. everything under the hood is tightened down proper. the timing is correct to. i cant wrap my head around what could be causing the light to come on. any help?

The only way to know is to have the EEC guide you by performing the diagnostic test:

http://www.turbotbird.com/techinfo/Retri..._codes.htm

Anything else is a guess.

thank you muchly