Re: Jet Chip
In my experience, those chips don't do too much. My friend has one for his Cherokee, and it didn't do anything but make it shift a little smoother. The chip is supposed to alter the fuel and timing curves, and it probably does, but the biggest difference should be the loss of $200 worth of weight in you back pocket.
Also, I think the chips are designed to increase upper RPM horsepower, which will not help in the acceleration oomph or off-road.