RPM Drops to idle intermittently when fuel tank is 1/4 full

[Monkey]

Hello, Just put in a new gas tank into my 1997 SN95 mustang. Used all existing components except for new filler tube grommet. Filled the tank - no leaks = win, problem solved right?
Not. When the fuel gage got to just under 1/4 a tank, the RPM would drop to idle while driving on the highway. it would coast and then re-engage to full rpm and the drive train would engage... a few more miles, same thing, RPM would drop to idle speed and I had no acceleration... then re-engage to normal. Acted almost like it was out of gas, but the engine never completely shut off, just RPM lowered to idle setting.
Filled the tank and no problems, ran normal.... This only happened when the fuel level was just a smidge below 1/4 of a tank.
Could this be a tank baffle issue, a faulty fuel pump, or something else. I'm not looking forward to dropping the tank again as it was a pain getting it back in when I replaced it. The tank is new, but the components were reused (new fuel filter though & new filler neck grommet).
Thank You So Much as this has the Mrs. worried and scared to drive it now....

 

[Neuron]

Why did you replace the tank? Since it started after this change it is most likely a result of that. I would check all of the lines and then I don't see anyway out of repulling the tank(I had to do mv '98 Cobra 3 times, got pretty used to it using a floor jack and piece of plywood)and checking out your work. Myself I would have replaced the pump while I was in there for peace of mind. You might also take pressure readings off the rail or using OBD2 software to verify.

 

[wmburns]

Exactly how much gas does it take to go from 1/4 tank to full?

Did you use a new fuel pump basket or service just the fuel pump?

Did you inspect the flexible line between the fuel pump and gas tank hat for leaks?

Did you inspect the fuel pump pick up sock to be sure it was clean and attached?

There are some small holes in the bottom ring of the fuel pump basket that are part of the baffle system. I could see a case where if these holes were plugged it could cause this symptom.

What I'm thinking is that the fuel pump is cavitating because it's not getting enough fuel covering the suction line. This is causing fuel to move but with too much air in the fuel. Any blockage or restriction of the suction line can cause cavitation