tried the car out again tonight. surprisingly the problem is gone. i guess driving on the highway at 150kph cruising speed in the pouring rain will cause some water droplets to slip through the filter and pass by the maf. my intake is placed right behind one of the airdams on my bumper.
i hope its just that...
guitaraholic, try your car out after a few days, maybe the water thats causing the misfire is all dried up by then.