hi there i have had an audi a4 1.8t for a couple of months now and having a bit of trouble with it. When we filled the fuel tank for the first time most of it ended up on the forcourt, when i looked at it found the fuel sender seal had been sucked in. So the leak was coming from there so refitted seal and all was good for a little while till car stopped, got out and took the fuel cap off big release of pressure so tried car with fuel cap removed and car ran fine. ive heard that the evap n80 valve could cause the vacuum in tank is there any way of testing this? if so i would be very greatful if someone could tell me how to do this.