Cop Tzer,
stage one doesn't increase boost all the time, it adds boost on demand. if you accelerate the car with only 25% throttle, boost will be minimal ( 0 - 5 PSI), at WOT it goes to 16 PSI but it drops down once going to a higher RPM range.
With the Manual BOV, it jumps to the set PSI and the drop is minimal. Also, boost will be reached at even 25% trottle. The computer will notice this and increase fuel to protect itself from falure due to lean conditions. The end efect will be incresed HP with low MPG but the engine could feel like the power is non-proportional or peaky. This was the reason I changed to the A'PEXi and later to stage 1. Now I keep my trusty Hallman on the glove compartment and install it at the track. once done, I take it off and get back my drivability.
Just Two Cents.
Ian
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