mine did the same, it was the MAF once i replaced it was fine, around £34 from euro parts, make sure it is a bosch, but now and again still did it, found the 1st lamba probe was gone, replaced that, seems fine now
but the first bet is the MAF, by removing the MAF wont make no difference, it will still drop, by unplugging the MAF causes this anyway on a perfectly working car.
best thing to do is just get a vag check on it, or try another MAF
OVERFUELING my 1st lamba probe was dead, when i replaced it the old one was black.
just get a diagnostic check on it mate, will save a lot of hassle.
also clean the throttle body as sicupra said.