Been chasing this one for a while, really not sure anymore what it is. My truck is a 96 T100 with 246000 miles (rebuilt motor at 175000) and just last week I've started getting a hard hesitation around 3000 rpm when accelerating hard. Basically the truck loses power for just a second then it comes back, making a very noticeable hard jerking. Also, the idle seems to be worse then usual, it starts up fine but once warmed up the idle will dance around from real low like 300 up to 1200 rpm randomly. Pulled codes and got a P0171 system too lean bank one. Checked for vacuum leaks and found none. Past few months replaced O2 sensor with denso part, replaced air filter, cleaned throttle body, replaced TPS, checked wiring for cuts and loose wires, and found nothing out of the ordinary. Hope someone can shed some light on this One. Thanks!