mass air flow sensor matey, its right next to your airbox can't miss it!! but to be honest i wouldn't put the 2.0 ecu and maf on a 1.8 unless you're changing the whole engine! i know for a fact about changing the maf's to a 2.0 when the engine size is less, and they make the engine stall and not idle correctly at all.

if you are going to put the 130 spec/2.0 cams in your 1.8 i would suggest getting your ecu chipped and remapped for the cams and for the whole engine to operate properly! or it could go so very wrong!