Well I recently put a boost gauge on my 98 a4 1.8t with 108k miles, and it surprised me to see that I'm at max boost only pushing 2 psi. I replaced the diverter valve, but I don't know whats wrong. Any suggestions?

 

here is my 2 cents.... I was running 13 psi when I got the car... two days later it drop to 9 psi... I replace the vac hoses, and still at 9 psi, finally my car stop at 20mhp , i found the rubber piece from the throttle body and intercooler piping had a 3 inches cut... when I replace the rubber piece my boost went back to 15 psi.. so I would check for a leak.. I hope that helps.