i would start with replacing your plugs. many many times i have had 4.6's and 5.4's with this problem come into my work. i always start with new plugs and 99 percent of the time thats the problem.
i would start with replacing your plugs. many many times i have had 4.6's and 5.4's with this problem come into my work. i always start with new plugs and 99 percent of the time thats the problem.
If it was doing it before the SC install, that more than likely eliminates the tune as well. Have you checked your EGR? Mine caused some part throttle bucking. Try temporarily blocking it off with some gasket material and see if the problem goes away. If it does, you need to either replace the egr, or do away with it. Getting rid of it will require a modification to your tune to turn off the check engine light though.
I've heard a few things can cause this. EGR like mentioned above, carbon tracking on your plugs caused by the gap being to large, and the COPs having problems.
Here is a thread that has a lot of links and info on the coils and wires and problems cured by replacing the wires/connectors.