Is it fully run in yet? As mine has had over a gallon threw it and I've still got some metal pinch.
That said I didnt feel the packaged pipe in my combo set feels as good as the JP4 does with the motor ............
The bottom end needle setting is VERY important with this motor and seems to bring the motor to life when right.
Mines set at :
HSN 4 1/3 turns out from closed and LSN 5 1/3 turns out from closed with the barrel opened. I'd suggest you try a little richer than though as there pretty on the mark I feel.
Otherwise I just spend some time with it getting the top end right, then lean the bottom a little at a time until you start the feel a lean bog on acceleration and richen it slightly from there.
Mine runs awesome and Sooo smooth, but it doesn't make power like my C6. I still preffer it as a race motor though
Rod