We have a '94 740i that to put simple, is nothing but a refined *****box. The car has had nothing but problems CONSTANTLY

. I'm trying to sell the car asap and tonight I have discoved an unusual problem. The engine is beggening to miss terribly. The car feels like it's only running on 4 cylinders instead of 8 and the power output is horrible due to this. I drove the car for about 7 miles before bringing it back home, and as I got out of the car, phew! Something is burning!!! It really stinks like rubber/plastic. I also noticed that the exhaust is REALLY hot. When you put your hand on the back bumper, the bumper is almost too hot to touch. Also, you can feel a lot of heat radiating from the driver's side rear wheel area where the exhaust is. A lot of heat too... WTF is wrong with it now??? I've replaced oxygen sensors and motor mounts within the last 7K miles, so those should be ok. Can someone tell me what could be wrong? Better yet, can someone just take it off my hands?... I'll let it go for $4000.
I could list all of the other problems we have had, but I don't want to waste a lot of bandwith...