My 91’ 2.5 is running kind of weird, it runs good for awhile then starts acting up. The check engine light comes on then starts miss firing. I will pull over check connection,hoses etc. I notice the exhaust manifold is red hot. I will let it set for a few minutes and it will run good again until it does it again. This little blue girl is my work truck and any suggestions will be helpful.Ive tuned it up set the timing at 8* changed plugs and wires.