[Showdown]

FWIW, and no I don’t run an IACV so take it with a grain of salt, but clustering my throttle body vacuum ports together in two banks (123, 456) and then clustering those into a manifold helped stabilize the MAP reading a lot. I’d recommend 1.) making the port hoses as small as possible, like 1/16” or 1/8” down from the 1/4” that they probably are now, and using a foam filled manifold (if you can) as it all helps limit the air leak to only what’s necessary and limits the pulsing that can sometimes wreak havoc on MAP signals… my guess is that might also mess us the IACV…