Well in terms of start off settings, do the quick math. 650's are 200 ccs bigger than 450's. 200/650 is 30.7%, so let's call it 31%. Set the SAFC at -31% across the board and you have stock fuel levels just like if you had the 450's in there. Taking 31% off 650 leaves you with the 450's, so you have a "zeroed out" starting point. Now, no "too much fuel" problem to worry about. You were overcompensating WAY too much by making it -50% when ou are in boost in hi throttle. You are now basicaly running 325 cc injectors at 16 psi on a turbo car. Way Lean, much knock, engine explode.

As far as O2's go: With 91 octane, you'd like to see .93 or so, give or take a few hundredths. With higher octane, that number can dip to .91 or so, and with race gas, into the high to mid .80's. When you are getting .75-.85 on pump gas, you are way lean. WAY lean and I can see why you are knocking. The 14b at 16 psi will likely need a few extra % in the small end (1000-4500 rpm) and even more fuel going up to redline. Tune the Hi settings first. It' easiest to set the lo and hi points at 20% and 80% respectively. Then once you have the car tuned for hi setting's just leave the low settings close to stock, or maybe a little richer than stock. At less than 20% throttle, your fuel trims aren't super important. You're cruising at that level so knock isn't much of an issue. Anywhere in between in partial throttle, the SAFC will create the proper trim based on an average of the lo and high settings for that point.