the throttle response is much better than the stock recirc valves. I "think" the stock valves leak boost until you get into positive manifold pressure. The stockers use vacuum to keep them open, so when you drive around easy they are open all the time while the HKS are closed. I understand that the HKS and recircs both use vacuum to open them, but it must be that the spring in the HKS is stronger so there is NO loss during low speed operation. I know this is a pandoras box but hey, I must argue from the seat of the pants performance gains I have felt.
I'm about to install sport600's on the car and I'm a bit unsure about using the single BOV's ability to vent 20+ psi and not damaging the turbo over time. It works great at stageIII and my stock turbos have not shown any signs of trouble after a couple years of hard driving. but I'm probably going to sell it and get a pair of greddy "type S" BOV's which can be vented back into the intake. I have switched back and fourth from the stock valves to the aftermarket BOV and it's quite obvious there is a performance gain. Sorry stock recirc guys!
