ac vent question

i put the ac to max or any vent setting and when i have my foot on the gas it goes to defrost but when i let off it goes to vent and then to defrost when i push the gas. WTF!!? i dont know what is up with it. i have a 90 xj with it converted to 134A. it really sucks and it kind of scares me cuz i think it might be a ghost. not really but it has me stumped. any help would really help

That is caused by a vacuum leak no ghost.
A good place to start is with the vacuum storage bottle in the front bumper, the line under the battery tray.

i bet it is. my cruise went out too so i bet its related. i thought the flap was cable operated.

When my 94 did that it was a rub hole in the vacuum tube going to the vacuum canister.