Oil light/oil pressure problem

I have a 97 2.2 sunfire.

I drive 25 miles one way to work mon-fri.

I noticed that when i get off the highway my oil light comes on when the rpms go under 1,000.

I bought and installed a new oil pressure sending unit.
-It did the same thing

So I went out and bought a oil pressure gauge and installed it on my dash and sure enough it shows the oil pressure going down to 0 from 25ish

So I installed a new oil pump.
- I still get the same thing....oil pressure is super low 5 to 0.
When i start the car....i get good pressure around 35...
but when i come to a light, slowly goes down to zero.
Along with getting off the highway...down to zero.

What should i do now?:banghead:

Thanks for your time!


Chris.