the timing might not be off, but the ecu might be retarding or advancing to timing too far because there is a sensor that is tweaking out.
As for looking for the leak, i've used starter fluid. and carb cleaner. (not at the same time) the engine will either race up or bog down. if the idle changes at all, then you've got a leak.
I'm not real good with abbreciations so I don't know what an fitv is. however the iacv, idle air control valve, would tweak with the idle. however, if the seal around it has gone bad, that might be your leak. if the valve was bad, then your idle would suck.
does it bog at a certain RPM, or at a certain load/throttle position?
I've worked on a single cam that would bog from 1/4 throttle to Wide open. It didn't matter what RPM it was at.
Hondas are pretty "smart" so if something is wrong and the ecu knows about it, it will retard or advance the timing as much as it takes to keep alive. But if it is something like a clogged injector, the ecu might not notice it, and the timing won't change (much).
also keep in mind when you are checking the timing, that the higher the RPM the more advanced the timing should be. Also, the further open the throttle is, the more advanced the timing gets.
hopefully, it is just a loose vacuum line somewhere. nice and easy to fix. (and cheap)
good luck