Occasional missing at idle

I'm just finishing up the final items (carpet) of restoring my project boat ('97 SN 196). One issue I've had since I first got the engine running (after two years of sitting) is that I get an occasional miss at idle. At the beginning I replaced distributor cap and rotor, high tension lines, plugs, I also ran a ton of injector/fuel system cleaners (several different kinds).

When I put it in gear (both to back out of the dock and idling out to remove slack before pulling up a skier, it will sometimes miss. However, as soon as I give it any throttle it smooths out and runs great. Also, occasionally it won't miss at all.

No clue what it might be but the only thing I haven't replaced are the injectors (that's been my suspicion for a while so thrown lots of injector cleaner in the tank.

Any suggestions on something else to look at? I never did a compression check before getting the boat because the last time the previous owner had it at a mechanic, they did the test and only one cylinder was about 10% lower than the others (my '96 with 1,600hrs had the same thing, but no miss--and engine manual says within range).

So I'm at a loss. Since it runs so well all the rest of the time (and sometimes when idling as well), I'm not horribly concerned. But I want to identify it and fix it.

Thanks in advance,

Gordon