check engine light just came on. i notice when stopped or idling the oil pressure drops to low until i hit the gas then it goes to normal

 

Two different problems. Need to see what codes are setting the CEL, the PCM really doesn't care about oil pressure.

Verify correct oil level, if that's good, replace the oil pressure sending unit.

 

Has your oil pressure done this before?
The pressure senders on these trucks are known for going out at this age. But you can't tell for sure unless you get one of these tester gauges:
http://t.harborfreight.com/engine-oi....google.com%2F
Its a mechanical gauge that gives you the real oil pressure.
Or have a mechanic test it for you. The sensor isn't behind the Intake, a pain to get too. Or you could put a sender in for the fun of it and hope it fixes your problem. But that's not what I would do.