2000 a4 apr stage 3 have been having low boost, 22psi is normal can only hit 15, found and fixed boost leak and reset ecu but no difference. On two drives I was overboosting, hitting 25psi pulling crazy hard then cutting boost, car was sometimes cutting boost at only 5psi. After a day of overboost back to 15psi, this happened twice in a week. N75 and*diverter*valve*are both fairly new. Can't find any boost leaks where do I go from here? No cel but just pulled p0140 o2 sensor b1 s2 no activity intermittent, sensors are new oem. Please help thanks

 

If anyone has any ideas on the B1S2 intermittant let me know as well. Son's 2001A4 just started spitting that code out after I just (<40 miles) replaced the sensor, which is a major pain in the butt since its the one on the back of the outlet side of the cat facing the engine. Bad connector or connection on the firewall, or at the ECM?