Don't believe there are any vacuum leaks. The intake and exhaust manifolds got a new gasket just last year, I retorqued just now anyway just in case. The only place I could possibly imagine an air leak would be in the carb mounting, but even that is only a year old and when I installed it I followed the guide word for word.
I have been through tuning it a bagillion times, usually always following the guide, but at times I have swapped jets, changed idle screws just to see if I could get it closer, but I can't. The last time I tuned the carb I followed the weber guide and that is how it is today. Don't get me wrong, she'll start right up and run fine, but somewhere something is lacking. I say this because I remember a noticeable difference in low end power from the carter to the weber. In every other test the weber wins, all except for the low rpm performance.