For a 2000-something Chevy mud racing truck, with full tube frame, turbo and nitrous stock 5.3L LS to begin with, and then later this (or something bigger) for on a stage 3 cammed 6.0L... what an absolute animal this truck should be, LOL!!!
For boosted air pressure throttle shafts/bores sealing:
So boosted air pressure from the air horn will go through drilled/tapped 1/16" restrictions at the rear of the air horn either side of the secondary accelerator pump shooter, down into the (unused, sealed) secondary power valve vacuum chamber, through passages cut in the secondary metering block gasket, to newly drilled horizontal holes in the main body that connect with the (unused) vertical secondary curb idle passages in the main body, down to the base plate, through the base plate "snake channels", then down through newly drilled 1/16" holes (throttle shafts removed, of course) to the throttle shaft bores... which will send boosted air (only) pressure to the throttle shafts instead of the mainstream way of sending boosted air AND fuel to the throttle shaft bores. This modification will eliminate boosted air:fuel from blowing out of the throttle shaft bores. As can be seen in the last picture, this boosted air pressure will be blocked from affecting the primary idle circuits with the front sections of the "snake channels" blocked with jb-weld.