on my SILs 96 tbird 4.6 there are 3 cats. The third one in the middle of the car has a rattle in it. Can we cut it off and just run a stright pipe? He has a cracked intake manifold where the heater hose connects to it and the car is blowing white smoke. I figure if we cut off the cat then we could see which bank the smoke is coming from and do a leak down test on it.