I have an 88 Cherokee and been getting bad gas mileage and did a new fuel pump filter but can here my fuel pump whining and fuel pressure is only 20 so fuel pressure regulator? All my lines were OK and filter is also new

 

A new fuel filter does not mean it is not faulty. One of my co-workers has a ZJ with the 4.0 that stopped running with no fuel pressure. He replaced the filter and it would run but with extremely low fuel pressure. After replacing the fuel pump the Jeep still had fuel problems. He replaced the fuel filter again and it runs like a new vehicle. The first replacement filter was defective.

Not saying that is your issue, but it is something to keep in mind as you check all other options.

 

Also check the hose for the pickup tube inside the tank for the fuel pump. My 89 project rig had a fuel problem that would not allow it to rev above idle. After starting at the fuel rail and working back toward the tank to find the issue I found that the previous owner had replaced the fuel pump and did not secure the hose properly. It had slipped off from the pressure of the fuel itself. After reattaching the hose and tightening the clamp it runs fine.

 

Everything is good just wondering if the pressure. Regulator is going out it runs fine