I did a timed run last night to see how long a full fill would run from top to bottom of the sight glass, I got a 1hr 21 minute run with the juice cut back to near minimal, oscillators wont run all that slow, but interestingly the engine on the left runs easier & at a faster clip, but the engine on the right will run @ less pressure.
Possibly a slight difference in pivot screw tension, or port hole diameters or positions?
So many variables in a situation like this, but so what if there is a slight difference between the two when running free. Put them both under different loads and they'll run however they need to in accommodating that resistance.
Another way to go might be to put exhaust throttles on both of them so they can be individually tuned and balanced.