1991 olds siera, has about 180,000 miles, 3.0

I started my car to go to work last week. It ran real ruff. Didn't seem to have the power that it had before. Went to the store the next day and the top speed was about 25mpr. Missed alot, went up a hill and it killed, but it did start up again. Went back home, top speed was about 15 mpr. Heard a real loud hissing noise, my husband looked under the car and found a hole in the pipe going from the motor to the cat. Converter. Now car wont start at all. Turns over, but no start. What do you think, maybe injectors? Thanks susyq47.[/B]