Volkswagen Repair: #4 Missfire i think, mass air meter, vw gti

Question
ok so i just bought a 2003 vw gti 1.8t from a Dealer yesterday. i noticed the engine light was on and mentioned it to the dealer he said he'd have the mechanic check it. so i put money down blah blah, came back the next day and finalized the deal and drove off with it, the light was no longer on. later that day it came back on blinking. i took it to my best friends and he hooked it up to his computer. and the code came back as pb300d i believe he said it was a miss fire. how much should this cost to have done? any kind of estimate?  

Answer
A blinking light is a misfire. A P0 300 is a multiple cylinder misfire an d may be a air fuel leak, throttle body, bad or dirty, Mass air meter, or multiple bad coils. If the fault is a P0301,302,303, or a 304 fault then that identifies the exact cylinder misfiring. If it is just one cylinder then the common fault is a bad ignition coil. Good luck. The car should still be resolved at the selling dealer.