bluB5sfizz

i have a 2000 s4 its got 165,000mi its stage 3 asp. the car has been acting weird sometimes it wont let me boost past 11psi, but other time the awe boost gauge says im getting 25+psi. when it hits that high of boost it makes strange noises out of the exhaust and the rpms jump up. its like the clutch is slipping but i dont feel its the clutch because i have a southbend clutch and i am very easy on the car no racing or launching. advice please!