Chances are, the weber will solve almost all of your problems now and in the future. There are modifications that can be done to the stock carb to make it perform much more efficiently even on par with a weber, (I personally still prefer the weber if you can afford one.) In all honesty, I feel that if it runs fine after its warmed up then it might be a choke issue. As far as other carbs, ive seen people use Holley carbs before and then there is always bike carbs which are great. But neither of those are as simple, easy, and complete as a weber. The weber is literally a bolt on kit with very few minor modifications need to be done.