2ltr Gt Help!

[Lukeyp]

Hello, after a recent trip to london my GT's backbox got so hot that it melted a holdall in my boot!! :( Has anyone any experience of this?? recently i had a hole in the backbox joint elded and i think it may be that now the exhaust is working properly the gases can't escape as the baffling has come loose?? The back box is squishy and there isn't a lot of pressure at the tailpipe. It is a 1995 'M' reg and the original ehaust. The car seems to be left standing before i bought it about a month ago and otherwise the car runs superbly. Was thinking of biting the bullet and fitting a powerflow backbox to see if it sorts it??

Thanks for any help. :)