X5 stalled/set codes while being inspected!

[workingonit]

Thanks Andrew, i might be catching a glimmer of understanding (maybe)- I filled the tank until the pump handle clicked off. The right tank looked to be about 1/2 full when I replaced the fuel pump, so adding 9.6g seems right (I was semi-sure that the tank would be over 1/2 tank, since I NEVER left my vehicles get to 1/4 tank...my wife didn't, but after three times running out of gas, she listened to me...oil pressure gauge inattentiveness cost her a Fiero, though).

"When people "in the know" realize their car is stumbling but happens to be near 1/4 tank, they will take a hard left turn to slosh some fuel over to the right and make haste to a gas station.

If you happened to be near 1/4 tank, hard turns can easily cause engine performance oddities as fuel gets shot out of the tank by the pump and tossed back in by a hard left turn.

If the fuel level is ≥ 27L the siphon is removed from the equation."

The stumbling incidents happened on both (quickly successive) hard left and right curves, so shouldn't the fuel level have already been higher in the right tank following the left turn, but on the next right curve, surely the level wouldn't have fallen too low in just that short distance?

I'm sure that I haven't let the fuel level go down under 1/4 tank in only 33 miles since fill-up (figuring as little as 5 miles per gallon, riduculously low, I couldn't have used more than 6.6g, so the tank should've remained at 73% or more full), so the siphon pump shouldn't be of concern, now?

I ordered another adapter for my fuel pressure gauge kit (the one I was missing has a bad O-ring, which is too small for me to replace), and a new tank seal gasket (in case I damage one) because I guess I'll have to pull both right and left side tank pump & sender assemblies before I find what's happening, but I'm waiting to see what pressure is at the rail, before I order a filter+FPR.

Looking at FCP, RockAuto, and Amazon (probably not the place to get one, from unknown middlemen), i see Bosch, Hengst, Mann, Mahle, and BMW filter assemblies. Listed in price from low to high. Bosch about $50, BMW about $250, but I'm always fiscally-constrained, so BMW is out of the picture. Recommendations?