V8 Headache

[CabooseKid]

I have a 1994 Cobra Mustang with the 5.0L v8 that has sat in a garage for the last 8 or 9 years. I have changed the gas; dropped and cleaned the gas tank; changed the oil, oil filter, air filter, gas filter, and spark plugs. I have also run the 2 part injector cleaner through it (the kind that only mechanics get). Here is the catch 22 on the car, it has trouble starting. If and when it does start it has a popping sound when I rev the engine and a black sooty substance comes out of the exhaust pipes. What is this stuff and how do I fix the engine so it starts smoothly and stops shooting the black stuff outta the exhaust. And what is this doing to my catalytic converter?