Is this something that just started happening, or has it been getting progressively worse over X amount of time?
Presuming you went through the AFM info in regard to checking the carbon tracking and such, I'd hazard fuel pressure or volume is the likely culprit.
If at all possible, you'll want to temporarily mount a fuel pressure gauge in a location where you can see it while driving to deterimine what's going on at the exact time it's doing the bad thing. (pressure should jump up to around 38-42psi when up on the throttle hard and around 32-36 when at a light cruise. In any event, it should not drop into the 20's unless you are doing some serious engine braking, and then it might not even drop that low)
Once you get pressure determined you can do volume checks to help decide if it's the pumps or the regulator. (good volume w/low pressure = regulator, poor volume w/low pressure = pumps and/or filters)
BTW, does this occur only when at half a tank and less of gas or regardless of the tank being completely full?
If it's of the 1/2 tank or less variety, it may be the stepped tube that connects the in-tank pump to the sending unit has failed letting the main pump suck air instead of fuel.
Another potential culprit is an internally roached soft fuel line partially blocking flow between the pumps or from the hardline to the rail. (blocked regulator return lines usually results in higher than normal pressure which wouldn't affect the engine the way you describe)
Presuming you went through the AFM info in regard to checking the carbon tracking and such, I'd hazard fuel pressure or volume is the likely culprit.
If at all possible, you'll want to temporarily mount a fuel pressure gauge in a location where you can see it while driving to deterimine what's going on at the exact time it's doing the bad thing. (pressure should jump up to around 38-42psi when up on the throttle hard and around 32-36 when at a light cruise. In any event, it should not drop into the 20's unless you are doing some serious engine braking, and then it might not even drop that low)
Once you get pressure determined you can do volume checks to help decide if it's the pumps or the regulator. (good volume w/low pressure = regulator, poor volume w/low pressure = pumps and/or filters)
BTW, does this occur only when at half a tank and less of gas or regardless of the tank being completely full?
If it's of the 1/2 tank or less variety, it may be the stepped tube that connects the in-tank pump to the sending unit has failed letting the main pump suck air instead of fuel.
Another potential culprit is an internally roached soft fuel line partially blocking flow between the pumps or from the hardline to the rail. (blocked regulator return lines usually results in higher than normal pressure which wouldn't affect the engine the way you describe)
