neither...first the maechanic is an idiot as the o2 sensor he is talking about if prop for the cat meaning its more than likely on or the other but i doubt its both at the same time. second if you dont like the sound without the resinator then keep the resinator.....third i only hollowed my cat out as they dont test the exhaust here but only do a site check to make sure its there...fourth tune the second o2 out of the computer or buy a sensor to fake the computer but if your getting rid of the cat dont put the o2 back in and no it wont make you run rich...last get the u bend delete or make your own as i did
