boost will react to heat rather than rpm. so if it is turning 4000 with minimal load the boost may level off... so adjusting the screw may not make any difference. i am sure some of these guys will chime in on this. i havent actually done it.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.