I have not done anything to it. There are no marks on the bolt heads on the engine I can see. Of course I played with the jetting a touch for local conditions. I can't remember the gears, but I believe they were stock when I looked it up after I had the chaincase apart for the driveshaft bearing replacement last year.
When I picked it up last year, it had 115 lbs each side on my gauge (sea level, all gauges read a bit different) when cold. I have not thrown my gauge on it yet this year. I may run to the heated shop where I store it and check in a day or two. My 07 600 RMK with over 2k miles has 120 lbs per side for comparision. I may also check another 600 I have access to with 1,000 miles on it for additional comparision. When I purchased it last fall, it had 4,200 +/- miles.
I was not worried about the miles when I purchased it since the 600 is such a reliable motor.