Dont just take the air restrictors out. Drill them clear and then put them back in so that gap isnt there.I noticed that once the air restrictors were taken out, there was a big gap between the source of the air and the dart. Is that what you're talkin about when you say to put foam in there and make sure there's a hole so the air can get out of?
They are talking about putting craft sheet where the cylinder meets the plunger, like on a powerclip. It helps form a seal while still allowing the barrels to rotate.