Yes you can I think they air on the side of caution because some maf are sensitive to some abrasive cleaners, so to cover them selfs tell you to remove the maf. I've done the treatment a few times but only once on my own scooby and I sprayed it into the inlet with the maf on. Just took the oil breather pipe off and used the hole it left in intake to put the straw in (pointing away from the maf and towards the turbo.