1967brutus

It does, and "chemically" (the amount of energy per cylinder charge, basically) it is less by about 20% for gasoline, which if that number is used as rule of thumb, seems to be fairly accurate in predicting what prop can be expected to produce the same RPM as on glow, if RPM/prop on glow fuel is known. But of course, that also depends on where the engine is operated in its RPM range, because engines become more tolerant to lugging down after conversion (in fact, they prefer it, it helps keeping temperatures down a bit).

Since AFAIK the output in HP is not stated for both your OS boxer as well as my ASP, I don't know either what the exact reduction in power is for this engine. the only indication I have is that the vendor that sold me my ASP told me what he had seen these engines do on glow fuel (about 2,3 hp between 7500 and 8K), and apparently the numbers he gave me were "straight from the box" and before break in, because although initially mine was producing significantly less than that (first runs showed something like 1,7 hp), after about 15~20 runhours it turned out that it only missed that 2,3 hp by about 0,1...
According to my prop-calculator (Pe reivers' propcalc), mine puts out in the neighbourhood of 2,1~2,2 if tuned for peak on the ground. (I tried different online calculators, with virtual identical results by the way).
That is not a tune that is usable for flight (too lean) but in "flight tune" there is still about 1,9~2 hp on the ground, which increases in the air due to unloading. For transparency: I tune about 300 RPM rich from peak for flight.
My guess is there is well over 2,2 HP availlable in flight. But that is just that, an educated guess. I have not yet found a propcalculator that can work with "in flight RPM" so there's no way to be certain...

FWIW: I have run a converted OS FT160 side by side with my converted ASP (I did the conversion on both, so there are no significant differences in the method of conversion), and there is no real measurable difference in performance. The OS is (much!) nicer made, but not measurably stronger or weaker in performance. Can't comment on the durability differences, my ASP shows zero deterioration, neither does my clubmate's OS, but he flies his a lot less than I do mine, so no way of telling either way.

Your engine might easily pick up a couple of hundred RPM by the way, when the running surfaces re-mate using the different lubricant. That is at least invariably my experience with engines that were run on glow fuel previous to conversion, that they pick up ever so slightly after 5 or 10 hours of operating time, especially if the glow fuel used to contain significant amounts of Castor oil. Apparently the type of lubricant has some effect on the mating of the running surfaces, IDK, but I see that slight gain every time again.