Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
If it is all set correctly then I would think it is the jetting due to the filter change more than the exhaust? I wonder do the sport version with the single pipe use the same jetting as the four pipe models? if not then that may be a starting point.
jetting for the F1 is 105 main and 40 slow.Den