Just bought an 07' Harley Davidson Saleen supercharged F-150. 40,000 miles. Truck had been sitting and after I drove it home started to buck on me. I purchased Motor Craft 515 spark plugs and installed them. I didn't reduce the gap and believe they come @ .045. Truck was better at first then engine light with cylinder 4 misfire. Changed that plug again. Fixed problem but truck still isn't running great but no engine light. What should I do? Thinking of buying the Autolite HTO plugs that were in it before I replaced them. Do I have to use the Autolite HTO? Or are they they the best? Also what should I reduce the gap to? Do you think my problem is the .045 gap or the Motorcraft plugs? Please help. Just bought it a week ago and nothing but problems. Thanks. Don