1981 Camaro Z-28 Exhaust Flutter once warmed up

I have a 1981 Camaro Z-28, obviously with a 350, and a rebuilt stock Rochester Quadrajet. It has run fine for over 2 years since the new cam was installed and recently it started running sick on the highway. There is a little hesitation from a dead stop, at about 2500-3000 rmps the guage jumps around and runs a little rough, and on the highway you can hear the exhaust flutter like it's missing. I have changed all plugs and wires, had the exhaust checked by mechanics, I changed the fuel filter, tuned the carb to factory specs, and I have run carb cleaner and heet through the gas tank. I did find that the starter wire from the battery melted to the exhaust shield, I had to pry it away since it welded itself to the shield, so I'm not sure if that shorted out and circuits... I have since then changed the alternator, still runs rough at certain rmps. I have run out of ideas on what it could be other than the carbureator? I have been thinking about putting an edelbrock quad 650cmf on it, but before I spend $300 on it I want to make sure it's not something else, cause it ran perfectly fine before this happened. Any ideas???:banghead:

Might be a cat starting to go bad?

it is defanitly the carb change it out for a demon they last forever i had a truck with a demon on it for 9 1/2 years with no problem at all