Reading Pathfider's heal skill it states you can use it with a healer's kit to restore hitpoints ("Treat Deadly Wounds") as follows (Pathfinder SRD):
You must expend two uses from a healer's kit to perform this task. You take a –2 penalty on your check for each use from a healer's kit that you lack.
When treating deadly wounds, you can restore hit points to a damaged creature. Treating deadly wounds restores 1 hit point per level of the creature. If you exceed the DC by 5 or more, add your Wisdom modifier (if positive) to this amount. A creature can only benefit from its deadly wounds being treated within 24 hours of being injured and never more than once per day.
The healer's kit itself gives +2 to the heal skill. Now - presume a character has a healer's kit but doesn't want to use any of it's uses up. Does he get a -4 penalty to the roll (as if he didn't have a kit at all) or -2 (from failing to use two uses of the kit but +2 because he has one)?