...when you update to propane, does it change the engine sound?  for example, an engine running diesel has a unique sound.  Does running propane have a unique engine sound?

Propane exhaust smells like forklift exhaust?

Diesels have a unique sound for a few different reasons, but a loud clacky diesel is usually because of where the fuel is injected or something, not because of the fuel type used.  And forklift exhaust smells exactly like whatever engine it uses, ie:  a diesel forklift smells like any other diesel, a gas powered  lift smells like any other gas vehicle, and a propane powered lift.... well, you get the point!