93 starts but dies
 

I have a 93 S10 pickup, 2.8L that starts but will only run 25-30 seconds. The only error on my scan is MAP sensor (33,34). I unplugged the sensor but no change. Don't know where to go from here. The truck had a burnt valve which I replaced (the cylinder head) but am not skilled enough to figure this out. By the way my grandson burnt the valve out, I get to fix it.