I have a 2005 FX4 with 35K miles on it. It has the 4.0 V6 5 speed auto. When I first got it, it would spin the tires pretty easily. Now it won't even make them chirp. It hardly even spins them when the road is wet. I've driven it like a granny since I've had it new. It does not drip or burn any oil. It still gets the same gas mileage as it did when it was new. It does not stall or hesitate and runs fine, just slow off the line. I saw the specs say something like 0-60 in 8 secs for this model. It does 0-60 in 10 secs now. I live at 6500 ft elevation now but I heard this motor runs great even at high altitude. Is there anything wrong with this?