Blocking off coolant to plenum

[LGAFF]

CCMANO, TOYVET and I did some country driving.....during the course of the drive I got left in the dust by Hans freshly ported intake and headers.....when we got to the car show Hans told me how he had blocked off the coolant to the upper plenum..........also Hans noted that you can now put your hand on the plenum surface and not smell sizzling beef......or in my case more bacony smell.......anyway, the question is, what would the anticipated performance gain be from this mod? Seems this would do well when combined with a relocated IAT, fresh air induction, etc.

Any thoughts? I am not talking 20hp but one would think it would have some impact.