spray can matt/satin paint jobs are always gonna have those streaks/linesthrough it.. to do it properly you need to put on a base coat of black then clear it, but use a matting agent in the clear,...
typical answer from a NA boy...you need a bov as it stops compressor surge which isnt good for your turbo.. without a one air goes back into the blades of the turbo and can damage the cartridge,...
i'd bet my car on it, my 180 had almost the same sound, i was running a t4 turbo with no BOV, my mate car was running a kkr turbo and it had a very similar sound to.. but you'll never get the same...
it may or may not have a code, depends on the dealer it was purchased from or if the previous owner put it on..if the dealer had set a code its usually on a card with the owners manual