The car is a 1996 GT, Ford crate PI engine w/ 15k. FRPP shorties, K&N, and dumped Flows. She sat for a few years (maybe 5 lol) and has been back on the road about 2 1/2 years now. Shortly after I got it back on the road, it started having fuel issues at anything more than 50% throttle, youd mash the petal and she would fall flat and almost stall out. Assuming dirty fuel lines from 5 years of bad gas sitting in it, I began to feed her a fairly constant dose of fuel system cleaners and regular fuel filter changes. The past 6 months, the problem had almost disappeared. Quick runs from stoplight to stoplight, 1st & second gear, accelerating to highway speeds, etc, she runs strong! But past that, I really don't drive her hard for any sustained amount of time. Last night I finally made it out to the drag strip for the first time in maybe 10 years. Anyways, I was pretty disappointed. I only noticed it in the middle of scond gear a time or two, but third is bad. It begins a weak bucking feeling. It accelerates still, but not strong. And the bucking feeling isn't crazy strong, just small surges. But it go worse throughout the night. Seems not to happen at any certain rpm range, but maybe more at a certain length of time at WOT. I reproduced the same effect today on the highway doing an extended on ramp run. My mind just keeps telling me its fuel related. The way it felt, the issues I ran into before, all my mind keeps telling me its fuel. The car is throwing no codes. The car really runs good under normal conditions, but the times I ran last night are driving me crazy and the fact that I have spent so much time trying to make this car 100% and then this! im just looking for outside opinions before I go dumping money into her. What would be a good way to clean the lines? The fuel pump is the 18 year old stock unit. Is this symptomatic of a pump going south? Or could there be something else that Im not thinking of??