boat misses on start up

i know this issue has been talked about a few times but my issue seems a little different.

1993 ski nautique 5.8 proboss. this boat has low hours like 350. she starts up just fine. idles fine , boat might dump on take off if not fully warmed up but that is nature of gt heads in a carbed boat so i live with that so im told. top speed is great 46 1/2 with oversized four blade 14-16. never misses on top end. last fall boat started to miss on take off 2-3 times on acceleration up to 34 mph.once up to speed all is fine. sometimes it does it sometimes it doesent. makes no difference if you try super smooth acceleration or hit it, sometimes it falters on either. makes no difference if tank is full or if tank is almost empty. stored boat all winter with stabilizer in gas. went out this spring and boat ran perfect the first 4 times out. once i got a fresh tank of gas in it problems started all over again. its like a complete loss of power on take off some times 2-3 jolts in a row and then it just gets thru it and up to speed in the course. once in a blue moon it will give a slight twitch of power loss, but very slight at 34 mph just into the course but only once.

had accelearator pump adjusted by mechanic last fall. put new plugs and wires in as well. boat has the coil packs so no distributer.
one local guy said anti syphon valve or check valve but my other mechanic said no way as i would have problems with top end if anti syphon valve was bad. other mechanic thinks in carb like power valve but hate to rebuild if thats not it. could it be electrical. if you hit the horn while perfect pass is engaged it restarts perfect pass while going 34 mph., but i dont see how that would cause anything, maybe coil going bad or computer???any ideas???