VW is sputtering in idle and in low gears?

I recently took my 2005 GTI to the local mechanic - I know the topic is up until 2004 golfs, but I don't think there should be much of a difference when you read the rest - So anyway, they replaced an O2 sensor, cleaned out my Mass airflow sensor, replaced the crank sensor and fixed a problem with the axle on the front passenger side and got an oil change. When I picked it up, the mechanic told me the spark plugs needed to be dealt with because there was wet gasoline on the plugs. Now it sputters a decent amount at idle (a shaking back and fourth at a red light that lasts longer than 15-20 seconds) and then upon turning green it sputters quite a bit; having power, then losing it. Kind of seems like breathing in and out really fast if that makes any sense. So he told me to go drive it on the highway for a while to dry it out. The thing is, this wasn't happening at all before. The idle was fine, it didn't sputter like this. There was some "laggy" gear shifting, which the crank sensor was suppose to take care of.

I suppose my question is, do you think there was something done wrong with the car? I haven't yet had the chance to take it on the highway for an extended amount of time.