adjust mixture on injection 8v gti

[brv172]

hi i have an '86 injected 8v and want to know how to adjust the mixture as it doesn't have a maf like all the images ive seen online it has the fuel line all leading to like a distributer on top of the air box. if anyone can help it would be much appreciated ta.

[Wayne]

Mixture screw is on the metering head but you need it running on a gas tester to get it spot on.