The magic number is something like 90% for dual/tri fuel systems.
Dedicated Propane/NG can actually produce MORE power if the engine is
specifically tuned and built - particularly with Propane due to it's
high AKI (octane over 100) of 115+
If i was only getting 90%, I'd be happy, I'm getting about 75% of
steady state, with only about 60-62% of peak.