My 99 and 01 have both done that.

 

Was your theft light flashing when you tried starting it>??? If so check your chip.....just because it went in there with clean contacts doesn't mean something can't get in there. I had that problem. No hard starting after hard driving though. Hmmmm.......... -Mat-

 

the sensor you were previously refering to was the cam sensor in the drivers side head in the front.

 

L started GREAT this morning, no problems
Think I'm gonna change the fuel filter this weekend, just in case (and cause it's due).

 

I use to have a particular chip that would not allow the truck to start on cold mornings. If I pulled the chip, it would start. If I put another chip in, it would start. It would act like the truck was flooded. I never really understood the cause, but it was specific to cold weather and that particular chip.