So after all this i take it back to my mechanic and told him to do whatever it takes just find the cause. the hollow pipe was more like a glass pack muffler. the inside deteriorated and clogged the exhaust. He dug it all out and the car finally runs. it just sounds like a mustang bc its all straight piped but I'm still going to go through and put in the cats and o2 sensors that the original owner messed with.

 

That's great. Keep your mechanic.