I've picked up a 1.8 TT Turbo Quattro which has been fitted with a K&N filter and dump valve by the previous owner. My (basic) understanding of how this works is that it should release the air when I lift off the throttle?
However, in the higher gears and higher revs especially, it seems to be building pressure then releasing every few seconds and even every second or so when I'm accelerating hard. This is causing what feels like engine surging (sort of accelerates in pulses) every time it makes the "woosh" noise and releases the air. I've just cleaned the MAF to check if this would help but I'm still having the issue.
Has anyone else experienced this? Or have a more advanced knowledge of turbos and dump valves and could point me in the right direction as to why it's doing this?