84-5.3 he, I believe I have a vacuum leak as under heavy throttle the blend door goes to the default defrost position. At the rear of the right intake I see 19 inches of vacuum at idle, Are there any Most Likely places to start testing?
Also, ARE all the extra vacuum devices- dump valve, and delay valve are needed. Can the vacuum advance be connected directly to the vacuum port?
Has any one changed the heater/ac control system to one the uses cables to control the blend & function doors?