Pulled the motor on my 2002 A6 4.2, to do cam chains, timing belt and a whole bunch of other things. There’s just one connector that I can’t seem to find a place for it’s seems to be connected pretty close to the mass air flow sensor, the big connector is mass air flow, little connector is the one I’m lost on all injectors are plugged in so it’s not an injector connector

 

Could be your vapour canister purge valve.