I have ran both series 2000 and the standard Amsoil synthetic.
I ran the series 2000 in my '01 Pro X 440 that was used for everything from sno-x to x-country to serious trail riding and never had a problem. As this was my race sled I went and checked and cleaned everything on a weekly basis. The VES always looked good and never needed much attention.
The standard synthetic injector oil was run in my wifes '00 XC 440 sp (edge racer) and worked very well. There was some carbon build up at about 500 miles but they were slower trail miles as she usually doesn't run it too hard.
In other words depends on what you ride and how you ride for which oil will work best for you.
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