'89 won't start when hot..............

Earlier I was having a charging problem, so I put in a used computer. Charging problem is gone. But....... now the truck won't start when it has been run for awhile. If I let it sit for 10-15 minutes, it starts fine.
Also, when it is cold it sputters when accelerating until it gets warmed up. Any ideas?
Someone said it might be the Coolant Temp Sensor.
Truck is a 1989 3.9 4WD

the hard start when warm could be caused by a clogged air filter or your fuel pump is getting weak or you have a leak in your fuel system thus allowing it to drop pressure.

I do notice a slight gas smell when the tank is full. Could that be the filler tube? - or what?