part throttle bog/hessitation/backfire

falling out of the air stream ,my 1985 suburban 350 would Ice the throttle plates on a 40deg or below day with high humidity
with a, heated intake, exhaust heat riser ,the only fix was to put the flex tube back on between the air filter and exhaust manifold and running a 195deg t-stat. I would come off the highway and the engine stalled out when stopping, when I removed the air filter lid the ice filled the bottom of the throttle plates.(just a thought)