Ford Repair: Sputtering, pump tank, fuel pressure

Question
QUESTION: I have a 2002 ford E250 that when I accelerate during a turn it seems to sputter and then if I put the pedal down to the floor it  smoothes out. Recently changed spark plugs,fuel filter,o2 sensors,air filter, etc. Have tried fuel cleaner but no improvement. Any ideas what it could be?

ANSWER: Two questions please.Is it diesel or gasoline?Is the check engine light on?If so,have the codes read please.

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QUESTION: It is a GAS 5.4 V8. No check engine light on.

Answer
Have the fuel pressure tested.But since the problem occurs mainly in a curb,jack the van up as high as it will go on one complete side when testing.You may need to test on the other complete side as well.If the test performs poorly on either side you could be looking as a host of fuel pump/tank related problems.If you do have to drop the fuel tank,Completely remove and clean it.It may have some type of vandalized obstruction.