i have an 89 s10 2.5 exhast manifold glows red when reving engine up. on 1990 Chevrolet S10

engine starts fine idles fine for about 2-3 min then idles erratic and sputters out tail pipe have replaced almost every part on engine. running out of parts to change. manifold will glow red with or with out converter and exhaust hhoked up have installed new dist and timing is correct 0deg per gm manual.

Asked by for the 1990 Chevrolet S10