cruise control

Model: 911, Year:1987, Mileage:90000, Type of use:Street use only
My Cruise Control accelerates when set then sags down below the set speed and accelerates back up, etc. This oscillation is similar the one described in a 10/30 2007 Q&A. You recommended checking for vacuum leaks and slack in the CC servo cable. I can't hear any leaks and I can't see the end of the vacuum hose that goes to the servo, but it seems OK. I tightened the cable from the servo a little bit.. The problem remains.The clutch switch is sticky, I have to pull up, just a little to get it to open before setting the CC. I can't see how that is the cause of the problem. It looks to to me like an typical unstable servomechanism in which it overshoots, then passes through a dead zone and then tries again to lock up, but overshoots.I bought a rebuilt unit from Programa. It was worse. It only worked in accelerate mode. I.e. if you released the switch lever after attempting to set it, it shut off!HelpHoward Salwen