Idle / exhaust problem

[jaimeson]

Alright, i posted this on bimmerforums but i'll elaberate more to my on going problem...My car idles rough and produces a lot of vibration (only at idle). II originaly thought it was a vaccum leak now it seems that I have some hesitiation in acceleation. Well on my way to autozone to buy some run of the mill vaccum hoses for my car my car suddenly turned from peepy to a deep throaty nascar sound. I looked under my car with a flash light a low and behold i blew a large hole out in my muffler. So that brings me to my next question...the car still idles rough, it has progressivly gotten worse...could this be a bad "plugged" cat convertor? Has any one had to replace there cat before? any problems or soultions to find out before i get hosed by the repair shop ( i would do it myself but I am sick of working on my exhaust and I really don't have the paitence for it) any suggestions are of cource welcome...BTW I am new here, I drive a 91' 318is with 135K on it

[Choking Hazard]

-I also have quite a bit of vibration- I'm thinking motor mounts.....

-Exhaust places are everywhere thanks to the big can era we are currently in.  I'm sure those guys can come up with a system that does NOT go pbtpbtpbtpbtp.  Is there vehicle inspection foir cars as old as ours where you live?  Those same exhaust people might be able to "remove buildup and blockage" for ya too...