Hi all. Need some help or suggestions to fix an idle problem on my 85 1.9 auto trans westy. Engine idles ok at start-up idling around 1100 rpm when ambient temps are around 80+ and around 2000 when temps are cooler 60s-70s. The bouncing starts when after driving on highway and engine is warmed up I put car in park or neutral then it starts revving up and down between 800 and 2000. It runs smooth at highway speeds and around town with no surging but at  stop lights or stop & go traffic and my foot on brake I can feel a slight pulsing. Within the past year I have installed new O2 sensor, temp II sensor, cleaned grounds and replaced some of the small vacuum hoses and plastic tubing. The plug for the idle adjustment has never been removed during the past 30 years so it hasn't been messed with. Should I be looking at the MAF next? Any help or suggestions would be greatly appreciated.
Spencer
85 westy auto