Update... I replaced the plugs today. Previous owner had Autolite platinums in it
and the dealership never changed them. So, they had been in there since I bought it last July. I replaced the cap and roter also, since they were both pretty shot. Reset the computer again after I replaced the plugs, cap and roter. Then I installed the 4.0l air box. The tube ended up about 4'' short because the throttle body is located closer to the air box on 4.0's. To fix that I cut the tube in the middle and slid in a piece of tight fitting exhaust pipe. Looks cheesy but it worked very well and it's a nice tight connection. Installed a new K&N and reconnected the battery. I started it up and took it for a long mountain ride and the difference was much more pronounced than when I first installed the chip. The problem was the crappy plugs and the very short air tube. I figure both of these things were counteracting the chips full capabilities. Also, the whistle from the 4.0 throttle body disappeared when I installed the 6 cylinder air box and tube.
So, in the end the chip was a GREAT improvement as were the other things I added and replaced today. I give the chip two thumbs up.