my b will run for about 2 minutes reasonbly well then falters for another minute carb and intake create a lot of cold water on outside then will finally quit changed out carb today with a dtlx 71 off my styled a r and changed mag with good hot mag off my b r will run if hold hand over inlet regulating air but stalls when try to increase rpm with throttle I am suspecting a crack between intake and right exhaust side of manifold as carbon build up on inside intake against exhaust side of manifold no vacuum to pickup fuel and will fire back through carb when trying to restart when warmed up any suggestions manifold gasket looks good