FOSHO94,
If you are smelling gas, and it is not leaking gas, then the car must be running rich.
When an O-2 sensor, or both, fail, the computer puts the system in a rich mode to prevent all the bad things than can happen if it were too lean.
Next, a failed IAB can cut down on the air and cause a rich mixture.
Have you noticed any black smoke coming out the exaust, or see a lot of "soot" in the exaust tips?
Injectors that are not funcioning properly can also cause a rich mixture, but this would normally be one or two injectors and should not cause the problem you describe.
If the Check Engine Light (CEL) is comming on, you should have a code stored in the computer. Check your codes. This will tell you the circuit that is causing your problems. I put it that way because a code for an O-2 sensor does not necessarily mean that the O-2 sensor has failed.
It means that the computer is not getting the "signal" that it expects from the O-2 sensor.
It could be due to a failed O-2 sensor, or could be due to a poor connection in the wires to the O-2 sensor.
If the O-2 sensors have 50k miles on them, then they most likely need to be replaced.
If they are relatively new, then you start looking for a poor connection, a freyed wire, a wire rubbed through and rubbing against metal causeing a brief short, etc.
I used the O-2 sensor as an example of how you should approach the problem, and diagnose the problem based upon the symtoms, the history of the patient, and the results of the tests you conduct. (A medical metaphore

)
If you just replace parts, you can spend a lot of money and the problem will continue to be a source of frustration, if you did not look for and find a poor connection! Hope this helps rangerj