Must apologise for my lack of knowledge, but what exactly is vag-com and what does it do ?:confused:

A simple Google or site search....

Ross-Tech: Home

you connect you car to your pc/laptop.....with a speicial cable..using speicial software

then

it'll read your ecu.....giving you insight into the goings on in car computer....helping you diagnose .....just like going to your local repair shop..except your doing it youself..........have a look at threads on this section ...that'l tell you what folks are doing with it..