Did you try pulling a plug wire at a time to really rule out ignition knock for each cylinder?

 

Sleeve knocks after the engine is really warm. Say after 10 minutes and driving a few miles.

If you have a knock upon start up - say in the first 30 seconds - it MAY NOT be a sleeve.

Could be lower end - rod bearing.

Before you spin a bearing, you can get the bearing shells for about $300 and put them in yourself.

IF you have a sleeve knocking at engine startup - that seems rare.
If it is 40 to 30 degrees out and you first start up and have a knock, probably NOT a sleeve.

 

Sleeve is more a metallic tick. Like a super loud valve tick.
I heard one in person when I test drove a rover with a sleeve issue.

 

Sleeves sound like a diesel motor, only they appear after the engine's warmed up vice go away like in a diesel. Perhaps an exhaust leak...would account for the noise and maybe the smell. Got an audio clip you can post?