I have the stock intake system and stock exhaust system on my S5 TII. I replaced the air box with a cone type filter and left the rest of the crap there. I recently got an ecu tuned for a front moutn IC and full exhaust. I installed the ecu and took it for a drive. Everything ran just a little more crisp, and the car actually pulled quite a bit harder.

So just to see what it would do, I disconnected the exhaust and put on a gutted downpipe, leaving everything after the downpipe disconnected. The car pulled unbelievably. I hit (peaked quickly) somewhere around 17psi of boost quite easily with the stock boost solenoid installed.

However when I disconnected it(stock solenoid), and attached my hks evc II, I found that even with it turned up all the way I could not exceed 12psi. Is there a reason for this?

I'm not trying to run 17psi on the stock turbo. I'm trying to find out why the stock solenoid will allow more boost than my $175 boost controller.

BTW I was running at 10psi before any of the mods.