You gotta start with the basics. Spark and fuel supply. And anyplace where work was done.
Also, if you did a carb rebuild, that would be a place to start, anyplace you did any work. If those carbs have the flow too low or too high, you may have a problem like that.
Could be the carbs need an adjust, or a sync.
But also, could be the leak at the fuel pump is an indication that it's losing pressure and just about out of commission.
You may have to turn this over to your local mechanic for a final tuning.
Good luck and let us know how it goes.
dc