Check Engine Light need some help

I drive a 95 S-10 4 cyclender 2.2L Standard.. After driveing for lets say about 10 - 15 minutes at about 55 - 60MPH my check engine light comes on. If I let the truck rest for any amount of time it goes back out... I've scratched my head as it is a odbi -1 and not a 2.. so the thing they use to check it is very hard to find around here. Ive checked the gas lid (as i hear it is common), Changed oil (it was about time for it
anyways) I'm getting ready to change plugs, wires, and distributor cap. Also, the Motor runs great, it doesnt knock, it doesnt run rough. It has 194,000 miles on it. I do know it needs a new heatercore (I bypassed it). Any other ideals that it could be?

OBD 1 codes can be checked with a paper clip or by going to AutoZone.

At that cruising speed is when the egr is working. I would just about say you need one, but have it scanned to be certain

I drive a 95 S-10 4 cyclender 2.2L Standard.. After driveing for lets say about 10 - 15 minutes at about 55 - 60MPH my check engine light comes on. If I let the truck rest for any amount of time it goes back out... I've scratched my head as it is a odbi -1 and not a 2.. so the thing they use to check it is very hard to find around here. Ive checked the gas lid (as i hear it is common), Changed oil (it was about time for it
anyways) I'm getting ready to change plugs, wires, and distributor cap. Also, the Motor runs great, it doesnt knock, it doesnt run rough. It has 194,000 miles on it. I do know it needs a new heatercore (I bypassed it). Any other ideals that it could be?

You should get the error codes before just changing anything. The codes will tell you in which direction to trouble shoot. Your problem sounds like it could be any number of things. Post beck your codes.