Doesn't matter if its fi , the timing wants to be higher at idle, like 20 btdc.
Especially if you have low cyl pressure.
15-16 isn't where I would run it.
That thing should have a controller and what you put in all the parameters as in you set the timing in the controller the way you're actually running it so if it's let's say it's 18 at idle then you type in 18 and idle and if it's full Advanced at 34,35, or 36 ...you set that parameter. You also have to set the throttle blades evenly and have that parameter set too... so of you want 800 rpm idle... you have to dial the amount the the throttle blades are open then check the feedback/numbers are within what it calls for. You have instructions? Read them., more so... understand them.