Loss of power in my 1991 Firebird Formula when check engine light comes on.

What is your question?

I did a full tune up on my 1991 Firebird Formula. plugs, wires, distributor, serpentine belt, fuel sensor. Now I have the check engine light comes on during normal driving when engine warms up and it loses power. Once I turn engine off and turn it back on it goes away as in reset mode then it happens all over again.