Cant get the heat shield off......

My Cat Converter. there are 4 bolts and they are completley rusted out. Used a 10m wrench which just rounded the bolts. Tried Vice grips, same thing. Sockets aren't working either.....Any suggestions? Should I try to heat them up?

there's a whole variety of bolt extractors out there. i'd say buy the drill bit lookign ones and try that. if all else fails, cut the shield off and buy a new one.