Best way to test Vacuum Leaks (popping noise)

[MandarinSixSeven]

Hey guys/gals:
I got my carb all tuned, muffler leaks all sealed, it has quite new spark plugs and wires, but I can't seem to get rid of this little popping noise on decel. It's not really loud, but really noticable and kind of annoying.

I'm thinking it must be a vacuum leak or something to that effect, or am I way off. What would be the best way to test? I know the timing is all good, I had that checked a while back. It has been doing this ever since I put on my 1406 carb, I was told it was a vacuum leak, but I don't know how to test...

Thanks