I have heard that sirios in general are very sensitive to adjustments. But that may be because they are very well manufactured and respond to needle adjustments very well!

I think the Fantom is a VERY good choice. I have read many rave reviews about it being better than OS CVRs.

I'd take a serious look at that and definitely get the 2 Speed Transmission.
that should be less than $200 and you can beat the heck out of em and say "Maybe I just drive better" lol

ram