I had that sound for my SF too...Watch out for the gas...I had mine filled at a Chevron station in a ghetto area..and guess what, the fuel was mixed with water...Bad fuel will create that scruff scruff sound...Try to run your fuel tank empty, and fill up with a grade 91 or 92 fuel...If the engine still makes that scruff scruff sound, try to use a 5W-30 Synthetic oil on the next oil change...that seems to quite my little baby down as well...
- I come, I see, I conquer...Then after 3 months of recovering from a broken body part, I'll do it all over again...