FASN8D, Hi, wait a minute! It's not necessarily VTA. The Turbosmart BOV in 50:50 Bypass mode will vent initially to Bypass and under more aggressive relief will vent excess pressure to the atmosphere as the piston rises further in the barrel. The screw in-out cap setting determines at what point this transition takes place. I'd say it is most likely you are in 50:50 mode, not 100% VTA, unless you bought the blanking plug that shuts of the bypass. It doesn't come with it as standard.
The BOV will NOT vary your power, unless it is incorrectly fitted or leaks. Too many users assume that somehow the BOV can be a sort of "tuner" device. What it WILL enable you to do is set the point at which the retained pressure in the plumbing is sufficient to enable the engine to get back on-song fast after a gear-shift, and yet not so much as to cause compressor stall.
If you are setting yours up, then screw it all the way down until it won't screw in any further (don't force it), then all the way out which should be exactly 6 turns to reach the red limit line engraved on the body and visible at the bottom edge of the cap. Don't unscrew any further from this line. Then screw the cap in progressively, no more than 1/2 turn at a time (I did mine in 1/4 turns) and test drive the car after each adjustment until you reach a point where you have no spits and backfires. Doing it over several days of driving in all conditions is best. The instructions that come with it are pretty good anyway, but my notes will add something that will help.
CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18