Just to update in case anyone ever reads this. So I put in the bolt on Magnaflow replacement and the problem is solved. Mostly. I think I may have done some permanent damage to the engine, because it seems to have lost a lot of power. There is also occasionaly a...putt putt sort of sound from one of the cylinders that beats in time with the engine. My guess is a burnt valve or gasket, but it's not always present so I'll leave it for now. Granted by the end I had learned to drive the car so lightly the code disappeared, trying twice to drive it up a mountain before I knew what was wrong (well the first time, the second time I knew what I was doing and did it anyway) surely did some damage.