GMC Repair: Cadillac Backfires, gmc vehicles, cadillac deville

Question
Hi!  I know your speciality is GMC vehicles and not specifically Cadillacs, but from the information I learned, I've notice that a lot of cars manufactured by GM, including the Cadillac, have had the issue I'm having.
So here it goes... I bought a 1990 Cadillac Deville last week.  Drove it home and didn't have an issue... a little hesitation, but nothing too bad.  But the check engine light was on.
Two days later we had an issue with the VATS security system, which we figured out.  After that the brake light came on and the check engine light went off.  Then I was driving it down the road and it seemed to cut out, like it wanted to stall, but if I let off the gas for a second and then accelerate it went.  After that it backfired on me and it seemed to work better for a minute anyways.
My uncle told me to check the Idle Control Motor... I think that is what it is called.  And we cleaned that and put a new fuel filter and air filter on.  And it seemed to run a little better, but it still cut out once or twice when I would make a turn and try to accelerate.  But we thought maybe it was just air in the fuel line and it would work it's way out.
So then this morning I'm on my way to work and it backfires once... and then about 2 miles down the road it backfires again.  This time it was very loud and then I heard scraping, so I pulled over and my exhaust was blown wide open at the seams.  But the car still stayed running and it actually seemed to run a little better... I didn't backfire any more and I didn't notice the cutting out like I had been.
Do you have any suggestions on where to start?  I'm a girl with little to no mechanical experience and before I take it in I want to know what is wrong with it, because I don't want to get ripped off.
Thanks in advance!!!!

Answer
This may be lengthy. I have worked on quite a few North-star engines. Cadillac uses nothing but North-star engines. These engines are very temperamental. They are prone to electrical problems. Depending on which state you are in, I would replace the catalyst (converter), which is on your exhaust with a high-flow converter. I would replace your muffler with a flow master. Tell them you want a quiet or hush muffler. You could also go with Thrush or Magnaflow brands for this. DO NOT go to the dealership, and do not put OEM or original equipment parts back on the exhaust.

 North-star are usually very good engines. But you must get on a strict maintenance schedule and adhere to it very closely. If you do this, it will serve you well for a very long time. Actually, I love the model of Cadillac you bought. Those are such beautiful cars.

What happened was the converter was clogged and the back pressure took the path of least resistance and ripped the exhaust. You will need to replace the complete or most of the exhaust. Later, I would have the timing chains (two) replaced. It could have cause a jump in time, resulting in weakening or stretching in the timing chains.

 This does happen on just about any vehicle. I had this problem with mine, last winter. Definitely have those things replaced and checked. But do refrain from OEM/stock parts on the exhaust.