I have a '99 f-150 with the 4.6L Triton. Last fall I had some spark plugs foul out so I replaced all of them. About two weeks after that my truck started running wierd again, almost stalling when I would come to a stop, but then catching and reving back up to regular idle. I checked the codes back then and it said O2 sensor, and "running lean on bank 1". At the time I parked it and drove my other truck instead. Now I am back to the f150, and when I push the clutch in and let it idle down, it drops to as low as 400 rpms, then revs up as high as 1200 or so, before leveling back out around 7-800. But then at that idle speed I can feel the engine misfiring.
I just checked the codes again and all it said was "running to lean" again, no problems with O2 sensors.
I changed the fuel filter last fall and have only put maybe a couple thousand miles on it since then so I don't think it is that. Injectors are pretty pricy, so I'd rather not have to replace all of those to track this down.

Any advice would be greatly appreciated. All I know at this point are the IDI diesels, not much of a gas pickup man. Thanks