Oil pressure gauge will drop if your engine is idling too low or choking.  That's not your problem, I think.  There are a few things it could be.  I'll list the simpler or easy things:

1. Dirty air filter - unlikely, as I would think that would be worse with more pedal

2. Clogged fuel filter - Again, I would think this would be worse when you ask the engine for more

3. Idle control valve - Highly Possible - It controls how much air goes around the throttle butterfly when at idle.  It's connected to the computer.  If it's got carbon build-up or is sticking and can't move properly, your engine will stall or sometimes rabbit the accelerator trying to fix the problem.  This problem happened to me- experience. It's at the engine end of the air intake next to the throttle- fairly easy to get to.

4. Bad Spark Plug or wire - This can show up at idle if the plug is in and out. I would check you plugs and wires.

5. Mass Air Flow Sensor - It's on the air intake and easy to get to.  If the little element inside it gets fouled up, your car will not be happy.  Electrical Parts cleaner spray can revitalize these parts, but if it's never been replaced, I'd replace it.

Overall, I lean towards #3 or #5.  A code scanner would help tremendously.  Most auto parts stores have these to loan out, and they're easy to use. Some stores will even run it on your car in the parking lot for you.  If memory serves, 1995 was the last year GM used that older computer, so you might be able to use/buy that scanner that is very inexpensive.  I hope this helps!