Original 1,8t 225hp maf has plastic frame+steel grid, which means crossection is smaller than S6 maf(instaled only steel grid), see attached picture. When rescaling MAF, should i have evalute area of plastic frame, or just measured inner diameters?

Sorry for my english(it's not my native language), maybe not cleary asked. That i wanted to say: BAM maf (left picture) has aditional plastic frame inside maf, which means real cross section area is smaller than identical ID tube cross section area (as you wrote - "Air does not flow through solid plastic"). Im going to instal new maf without plastic frame, so rescaling only by ID works fine and difference by plastic frame will not affect anything?

thanks