88 Ranger 2.9L oil light flickers at low RPM

[SalsShittyTruck]

Hey all.
Tryna discern how much concern is called for in this situation.
Recently replaced the oil pressure switch (just under the head on the drivers side of the block. one wire sensor) which fixed a constant-on oil pressure light. When the sensor came out, a nasty plug of sludge came out behind it. Looked like the worst blackhead ever.
With the new sensor, the oil pressure light flickers at low RPM (idle or braking).
Think it has got 10w-40 in it, and the average outside temperature here is about 100F.
Thanks for any suggestions or tips... unless they are stupid.

 

[410Fortune]

Remove the sensor and install a mechanical gauge so you can see what your real oil pressure is
Sounds like loss of oil pressure due to sludge buildup in engine
Diesel oil for a few changes might loosen some sludge and regain oil pressure
First mechanical gauge so you can see actual PSI