To protect myself, I have to start by saying federal law prohibits what was done to the converter. Now, since the converter isn't functional, the O2 sensors can't work properly. Basically, they tell the computer what type of pollutants are being put into the air by measuring the temp and conditions of the exhaust gases. Based on what the sensors say, the computer will compensate by making the fuel mixture richer or leaner. Now, if the computer thinks they are not working, it can go into what is called a closed loop. At that point, it makes the fuel mixture as rich as it can just so you can make it home or to a shop.
With that said, you mentioned that it feels like it isn't getting enough fuel. Have you checked the fuel pressure to make sure it is within the manufacturer's specs?