I was subject to "testing" injection of butane just below the venturi on heavily laden motors trying to operate on low to mid eighties octane Pemex gasoline.
The results are twisted. Try to stay with this...
Preignition and detonation was eliminated prompting returning initial ignition timing to factory setting from ******** 4 to seven degrees.
Added Propane occupied space used by gasoline and O2.
Net result was a noticeable decrease in horsepower as compared to an engine operating on straight USA gasoline. Engine coolant temperature had a radical decrease from effects caused by retarding the spark.
How does, and in what manner does or can a programmed ECU internal combustion engine benefit or profit from a radical fuel change? Change O2 properties the engine control will compensate or at least try to. Same for HC and CO.
Frankly, and I do not say this lightly...
I smell a rat...