Now that I have your attention.....
I had been experiencing a bad misfire under load (not necessarily on boost either) and decided that it was time to change the plugs. 160000 km on the odometer, (I bought it at 60000 km) so it was long overdue. Old plugs were found to be quite fouled and worn, so that was definitely the main cause of the poor performance.
Tech at the dealer is a Roush specialist so I felt that I was in good hands. After plugs were replaced (torqued correctly - I even left him a reminder note), on-road diagosis found a random misfire on the front two cylinders on passenger side and the front cylinder on driver side (1, 2 and 4?). Misfire only happens under load (again not necessarily boost) and doesn't raise a code. The tech swapped COP's and injectors around per normal practice but the misfire stayed with these three specific cylinders. Hotline advised him to clean the MAF which he did with some effect. Had them check for vacuum leaks and none were found. Told the shop not to go any further, (their hourly rate is a crime) and that I would drive it for awhile and monitor the performance.
The truck accelerates great now - very smooth with a lot more kick and cruises great, but on occasion there is this little hiccup that can be felt only under load as described above. I don't punch it unless I'm merging onto the highway or have to pass on a hill.
Truck is completely stock. I'm wondering if the problem is electrical, originating in the PCM. Anyone else experience this phenomenum? Any thoughts on the electrical being the problem?
Thanks,