Rough running on 1/4 tank or less

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Todays new problem!! The last couple tanks I have noticed that once I get down to below 1/4 tank or so I will experience similar start up symptoms as a IP seal. It will fire up no problem but then sputter and shake after a few seconds like there is air going through the system, give it some throttle and it will steady out and be fine. There's no vacuum problem on the tank that I can tell because when I open the cap it doesn't go "pppsshhhhhh!!!" I've only noticed it since the weather warmed up, anyone have any ideas? Oh, also, I change my fuel filter every other oil change, it's almost due for one but I can't see that being the issue.

[yojimbo]

Pinhole in the pick up pipe at the 1/4 full height. Next!