Ignition system problem? Help!

Next time it dies, while loosening the gas cap, - listen .. if you hear/feel suction at the cap, perhaps the gas tank vent has been plugged, causing vacuum in the tank,, and will run till the tank vacuum exceeds fuel pump suction,, and dies,, for a while.. hope its this easy..

Did you plug any hoses when you took the old carb off ??

When it blew off the vacuum hoses,, did you plug something you shouldn't have.