Hello all A while ago I had some advice from a few of you after my newly purchased S3 (APY) seemed to be loosing boost ,obviously the advice was to get a smoke test as a split hose was likely. Couldn't find anywhere local for a smoke test so I made a DIY boost leak tester and found a hole & a split in a PCV hose so thanks guys but here's the problem - The DIY guide says to remove the oil cap to stop pushing oil into the hoses but when I did this it would not hold any pressure, non at all!! As soon as I tested it with the cap back on hey presto it works, I only dared to put a small amount of pressure in though but it did help me find the PCV split Now it picks up better and idles a bit better but at around 3.5-4k the power trails off and eventually picks up again so I think I either have another boost leak only showing at higher pressure (and the turbo eventually spins faster to compensate) OR maybe the PCV valve is knackered which is why the pressure test wont work with the oil cap off, also on idle if I remove the cap a fair amount of air pushes out against my hand. Anyone know if I'm barking up the wrong tree with the PCV valve as I may have got how it works all wrong! I could just go up to about 10 PSI with the DIY pressure tester but am worried about pushing oil through as I have to have the cap on. Forgot to mention - Sometimes while accelerating a hear a hissing from behind the dash passenger side, same noise as the DV but not as loud, always done it so not sure if that's normal. VCDS shows the boost does lag behind requested until eventually slightly overboosting(not enough for limp), Also the MAF readings are very low averaging about 145-160 (Car is remapped) Thanks to those who managed to read all that & hopefully someone can help point me in some sort of direction!