MIL lit on 2005 passat glx wagon...and it's running "putter-y"?

ok for starters what type of engine does it have in it ? 2.8L , 1.8L, 2.0L, excetra... this will help problem solve the issue. Also first thing i would check for a emissions issue is get your hubby to roll under the car behind the drivers side wheel and look for a 1 inch pipe that comes down and goes under the rear subframe and leads to the front of the car. This line is a comman rot out in these cars and it should run from the charcol emissions can.

"Putterning" makes me think that the car could be misfiring. A GLX should be the 2.8 V6, so that could be ignition wires or coil. Sometimes an ignition wire, when removed for inspection, can have oil coating from an internal valve cover gasket leak, so that should be addressed along with the wire if that's found to be the problem.

Might clean the mass air flow sensor housing and air filter change.