Increasing the IFRs is the wrong way to go , these are fitted with .037" & need taking down to .030 @ least , the IABs are around .067" , i had a Demon on 500" which pulled 16" vac , the IABs came out to .062" with IFRs @ .025 , the throttlke blades were also cleaned up , put a .050" restrictor in the trans feed also (.080 stock) , if you move the IFRs to the lower position in the metering block just watch out for any leaks between emulsion well & idle restrictor as there's not much material here , best thing is to keep the IFRs @ the top.