Sounds like one of your cylinders is not firing and the cat is exploding the fuel. You can try and use an infrared thermometer and check the exhaust manifold to see if there is any temp difference--that would be the bad cylinder (either compression or spark). If it is only very occasionally, it is much harder and an inspection of the plugs may tell you--it will probably be more subtle or you won't be able to tell at all.
If there are no indication, start with a compression test. If they are all in range, you may have a bad plug wire , fuel injector, or even an alternator that has a zenier diode going bad that bleeds A/C into the system and can cause misfiring fuel injectors.
Maybe this helped, maybe no. No easy answer from me, plus I am really tired and have been drinking and it is only 7:30 on tuesday.