EFI L-series stumbling issue

[artrixx]

got an EFI L-series and today its started an intermittant stuble when you are in the low rev range, car doesnt stop just stumbles and sort of feels like its not running on all cylinders for a couple of seconds then its fine. never seems to happen when you are acclerating hard just when you are slowly getting away. wondering about fuel pump maybe coil or leads. went looking on the american site and someone mentioned a maf sensor that may need a clean with electrical cleaner. car is only new to me and i dont have a manual for an EFI just where is this maf sensor and does anyone think a dirty one could cause this sort of issue. car is a touring wagon 1989 model. cheers