I have tested with them fiitted the other way around and I did NOT work any better, infact the power was down. upto 3psi of boost was lost on 2 AUMs and 1 AGU, plus there was an ARZ which was 7psi down comapared to the other way.
The problem is the boost pressure pushing up on the based of the DV piston, and the pressure that is comming in from the top cannot keep the piston locked down 100% so the piston opens up a fraction and bleeds the boost off, same with the Split-r valve.
This is not down to the Forge valve they work 100% the correct way, The problem is down to slight pressure variations in the pipe system.
Even a small pin hole in the smaller vacume / boost pipes will allow the DV to open right up when the pressure is pushing on the spring..
Fitting the DV the "correct" way puts the positive pressue on the side of the piston and does not put any pressure in the base of the piston or the spring.
I am not the best person to put my thoughts in to words, so I hope you can understand where I am comming from with this one?.
Nick