OK this is my first 4.6 car, I am mainly a 5.0 guy but I got it in on trade. What the car is doing is when you step on the throttle wide open, the car does not seem to pull the rpms very quickly, at it kinda hesitates around 4000 rpm's and once it does pass 4000 the car is already pinging. The car is stock other then a K&N air filter. It has 99.000 miles on it, and has no other problems what so ever, the car was well taken care of. I just put a new fuel filter on it thinking that might be it, but the one I took out was not plugged at all(I changed it reguardless). Any thoughts what so ever will be a big help to me, I am looking to sell this car, and I want to get the problem fixed. The wierd thing is, is that normal driving you would never know it hesitates or pings, until you really start to get into it. Please help.