I'm typically .070-.090 on the tree, sometimes I squeeze a .050 out. I think twice I've been better than a .050 but that was pretty much guessing or pure luck. When I run with only the 2bbl I run with the secondary wired shut that way they don't happen to open their selves inconsistently.
It sounds like when you say you are running a 2 bbl that you are actually running the front half of your 850 4 bbl, if that is the case then perhaps a much smaller 4 bbl like maybe a 600 or 650 would give you what you are looking for. Probably have better throttle response and power than half of an 850.
