I'm going with a timing problem as well. Have you or the shop verified timing with a light? Doesn't matter what number is in the timing cell if you're off of TDC. Also, I'd look at the timing dwell. If that's too low, the spark will be like that of a Briggs and Stratton 2.5HP. I run the dwell at 3.5ms on the LS D585 coils.
