I work on 2 of these- sounds like maybe the fuel injectors are acting up. Sounds kinda stupid but what I do if I suspect the regulator's running too much pressure is to slightly raise the engine rpm in neutral & shut off the propane tank & listen to the rpm of the engine as it runs out of fuel. If the engine seems to "clear out" & run normally just before it runs out of gas the system is rich. If it just stalls with no rpm change before the stall then the richness isn't because of a pressure issue.

I've had ALOT of problems with the injectors in the 2 I service- customer refuses to change LP provider. i'm always having to clean/replace the injectors so the unit will run correctly.