I just recently bought a 2003 audi a4 1.8 turbo and have had a couple codes pop up & also epc light come on with trouble starting & dying out. The first time i checked codes it was p0299 turbo underboost so i took it to dealer they said turbo was ok but the solenoid purge valve wasnt getting pressure so i would have to change & see if it fixed the problem. Didnt do it as it was about $300 to fix out of my budget so was planning to try & fix myself still havent replaced it yet. So i cleared codes then recently i would start my car & would have trouble starting first time turning over then EPC light would come on. Cuts out sometimes at lights but after i turn off & restart it would go off & be ok. Happens every now & then. Checked codes & 2 different ones popped up now p0456 & p0442 (evaporative emission system small leak) for both codes same discription. Does anyone know if these problems/codes have anything to do with eachother? Might the solenoid valve be causing any or all these problems like the dealer said? Ive checked forums & seen it could be mass air sensor , crankshaft position sensor, or epc sensor at least for the EPC light problem or could the solenoid purge valve be causing all 3 codes? Any suggestions?