A little while back it was mentioned on here that a mechanic solved high HC on a emissions test by using some kind of black stuff around the intake hose where it connects to the throttle body.

I found that there is a sheet of gasket material sold at most chain stores. I cut an inch wide piece off the end of the sheet I bought and wrapped it around the throttle body to measure the cut. The stuff will rip if your not careful but I got a good piece made. Had no problem getting the intake hose (used original volvo cleaned with degreaser and rag) to fit over the gasket material. My car has performed with a much softer pedal on accelerations meaning it has more power. The idle which had been low and erratic has now stabilized except when I first start the car in the morning. It won't die now but it struggles the first bit. Thinking maybe I need to change the filter on in-tank pump since my main filter has been replaced multiple times due to either rust or a build up of dust like from a dirt road in the tank.

Anyways, a sheet of the gasket maker is about $6 but its an item I plan to use every time I take off the intake hose. Enough material for at least 12 self made "gaskets".

Butyl Windshield sealer... a small dab on the metal surface will spread very well and doesn't harden...
Also if the main duct after the AMM develops holes... squeeze some Gorilla Glue (original expanding version) into the holes and allow them to expand. I've got 2 of them working flawlessly.
--
'92 244 w/ M47 (Hydra, ipd bars and springs, bilstein, urethane bushings)

I've not had this issue yet - but wouldn't a good bead of the high temp gasket sealer (silicone) do the same?

Seems to me if you put this around the throttle body throat - and a little on the hose - you'd get a good seal (especially when you add a clamp).

I didn't want to add anything that would make a mess so I went with a dry material. Silicone damages the O2 sensor so I worried about anything that might somehow make its way into the throttle. Small chance but thought it might be a problem.

I'll have to try the the original gorilla glue for any other holes. Even if one doesn't suspect a vacuum leak I think having some of this material in place would put any fears to rest and might just improve performance when you thought performance was good.