You said earlier that the timing problem was fixed and then you said it was 10-15 off. So which is it?
If you have a double image you may be able to eliminate this by tuning the bike. New points. You can not gap old points. You can not file the gap like we used to years ago. In today's world it is new points every time you turn around.
If you do have a double timing image this must be fixed before anything else can be attended to. This is the article on Duane Ausherman's pages that tells the story about the dual image on /2es. They are a lot different but they are also a lot the same, these old bikes and ours.
That article is really hard to find because Duane's index isn't very useful, IMHO.
Vacuum leaks are below the carbs and cause poor performance and bad idle. They seldom cause a miss at speed.
I know I sound like I'm yelling but I just talk loud.