Situation: Round about 3700rpms and about 1/2+ throttle the car tries to shift but doesn't complete it. Kinda like the tranny knows its time to shift but the engine isn't producing enough toque (Power is fine at less rpms).If I keep on the gas (only did it for a moment)the engine slowly gains rpms but speed remains constant.

History: Had this happen before. Took it to the halfa#$ dealer in Daytona. They said "We think it might be bad gas (Miserable fuel quality in the south). Try some DryGas". This and a fresh tank of gas at a brand new Chevron worked like a charm. Today, 3 months later, it starts doing the same thing. No problem, add some DryGas and a fresh tank of Chevron, but it is still messing up.

Checked: Tranny fluid level fine
Car serial # isn't on the TSB list for tranny ecu
No check engine light

Question: What is happening?(I know AutoTragic..) Could the fuel filter in the tank be clogged and if so how do I replace it?