Engine Performance problem
1996 Chevy Van V8 Two Wheel Drive Automatic 120000 miles

I have 96 chevy g20 van that is giving me all kinds of problems.
Right now it stalls at idle and buckles at highway speed. Check Engine Light is on with code p0118.
Fuel pump has been replaced but it didn't fix the problem. There also was a leak on the upper intake gasket which was fixed/replaced. New water pump and new coolant and new transmission. I really don't want to throw money at it buying different sensors and such and would approciate if someone pointed me in the right direction.

Test the coolant temperature and the throttle position sensors and also clean out the idle air control valve.