whipple,nozzles

talked to a guy at lysholm tec. here in sweden ,he said maximum rpm on a a980 blower was 19000 rpm.recertifying is made by them every 3:rd year for1000$ for that price they canged all bearings and seals.Has anyone been at 85-95% with a whipple,what kind of boost pressure should i get with a 451 tad style fathead5 engine?why have 2 nozzles/port ,is it to get more volume or is it fine tuning of ex.temps whith checkvalves.I also have seen something called psi mod on barrelvalves, is there a whipple mod and what have been done to them?