So I have a 2014 Wrx stock except Tomei exhaust and Turbosmart BPV and today I installed a Prosport boost gauge. When everything was finished I started it up and at idle it sat at -28/29 Hg and full boost it was at about 12psi. Is that normal? I had a turbo Mr2 before this and I never remember it being that low. Also on my test drive, I noticed that the car was backfiring a bit under light boost loads. Things weren't right so I went back and checked all the line to make sure nothing was leaking and it seemed good. I went for another run and the same thing. Then I thought maybe it was because of the BPV so i put the stock one on and still reads the same. Any ideas?