high idle in neutral only

Excuse me. Baby Boomer who knows not how to converse in a forum, or any tech fashion. Getting desperate as young mechanics have never seen a carbureted vehicle. Love my first new car, 85 FWD/4WD GL wagon 1.8. Cannot get to pass smog with high idle in neutral. New Cat Converter and replaced a broken vacuum hose. Could not even remove air cleaner as it is stuck on. Is on 3rd carburetor and last mechanic to work on it said idle set as low as possible. I've moved and he may have passed away by now.  Smog inspector suggested vacuum problem but cannot really converse due to rules. Read about a possible Intake Manifold Gasket leak.Idles and runs smooth all the time and gas mileage not changed. Have yet to find someone here who knows carbs and it may be unrelated? Idle starts at the 700-800 it is supposed to, but immediately increases for warmup, BUT never drops back down. But if put in first on flat ground it will move out at the 800 rpm , only to rev up to 1500 each time the clutch is disengaged or parked in neutral.  High idle was 1300 before a snapped vacuum hose was replaced.  If anyone has an idea I hope I can find the communication !    Every comment I found online speaker to idle dropping too low when taken out of neutral but my car is opposite. Perfect under power but smooth and too high to get smog test when in neutral.