Billet intakes work well for bogging down too- totally ended the problem here when I was still running older standard NT 50 carb with the 66 kit it came with-
Now I use the billets with NT 66 Speed carbs on both my bikes- nothing expensive or exotic , and few problems ever.
Boygofast on ebay is about cheapest for Speed carb- billets at Pirates and Piston- about $20