I have a 03 660 grizzly ive been fighting with for 3 years. I put a bbk and stroker cam ignition and a used hmf slip on on it. Its not a swamp series just a regular slip on with packing. Ive been fighting with getting it tuned right it would always spit and sputter when i can it ans not come out of it. So i got fed up and brought it in to get done. The guy told me that the slip on is junk and it will idle and die cuz theres no back pressure. He said to throw it away. Anyone have this issue?