so i have been trying to hunt down what the cause is to my 2001 s4 losing psi from 4300-6500rpm...it goes from 14-15psi down to 10 or 11. I have replaced and checked all the hoses that are part of the intake/intercooler system and all of them are tight and show no signs of leakage. My shop said it could be a valve, but i would like to see if anyone else has had this problem before i go and buy the 200$ valve. i dont have a check engine light on either. this is extremely frustrating so anything helps! thanks.