Hissing during acceleration
 

98 A4 2.8QA that sounds like a snake when accelerating. doesn't seem to do it while parked and revving. i've been dealing with it for a while but now i'm starting to notice a lack of power especially in the lower registers. any ideas as to what this could be?

Possibly a vacuum leak. Check around the intake and SAP piping, as well as the vacuum lines on the solenoid panel on top of the engine. Might just as well replace them - they're likely brittle and could stand to be changed. Only takes about 45 minutes to do all of them.

i've checked what vacuum lines i could.. is it possible for the suction pump to make this kind of noise? it sounds almost spitty