About 6 PSI. I have spoken to John at Alpine Developments and he indicated that he has had similiar problems with the S/C that are running 5 PSI or higher. He also felt the frequency clamp would resolve the problem. The problem is that I live in Park City and have to drive up a steep 10 mile grade each day from Salt Lake City. On the dirve up, the S/C is under full boost for quite awhile and the MAF reads a higher them normal flow rate through it. The OBDII scan tool indicated that the fault code is on the high frequency parameter which is due to higher then normal flow rate going through the MAF. I spoke to Split Second and they feel confident that the frequency clamp will resolve the problem. They just needed to know what the frequency range is and whether it was registering a fault code on the low or high frequency signal to the ECU. I'll keep you posted on how the fix goes.