Recently my truck started doing this thing where (not all the time) it will sputter when letting the clutch out and jump like it's being let out too quickly, even with the clutch completely out. I have been driving this truck for 4 years, so it's not my driving style. I do have an exhaust leak at the manifold though. Could that be causing a loss in back pressure or something? If that's not it I'm pretty much at a dead end here. I thought it might be a clutch issue at first, but it's still shifting fine and engaging smoothly when I'm not having this problem.

 

My cousin had a problem like yours with his truck. It turned out to be a cracked intake tube that was sealing at idle, but when the clutch was let out the engine would twist some and break the seal. This caused some air to be temporarily unmetered. Also check any wiring and hoses that could be doing something similar.

The exhaust leak could be allowing air into the exhaust that the o2 sensor is reading as a lean mixture, but I doubt this would cause the symptoms you are having.

 

It could be an exhaust leak but you can check for other air leaks with a can of carb cleaner and spray it around the intake while its running. ALWAYS wear glasses when doing this. If the motor races you found a leak. As far as exhaust goes. You might be able to score a manifold form someone here that has put a headset on. Just a thought.

 

I cleaned my air filter and it seems to have helped a little. I'm replacing my exhaust gasket when I put in my headers so that should pretty much fix it if thats the problem.