95 Toyota Previa burning catalytic converter Gaskets?

I had a leak, changed the flex/cat converter, sounded fine. Then I lost power, so I needed a full tune up...did a FULL tune up, fuel filters PVC air and oil filters new wires and plugs and even the 02 sensors for the cat, everything was fine THEN my defog and heat would make the car lose power and the rear defog wouldn't work and I burned the Cat gaskets and I have a leak AGAIN???? WHAT is going on this is all in the matter of 2 months...??? I think my Cat is burned and the gaskets are burned as well? WHAT IS GOING ON?

did you put a factory Catalyst/flex pipe assembly on. It is unlike the factory setup with the good flanges to develop a leak again but have seen problems with the aftermarket stuff. If the engine was missing, that could cause the converter to overheat and burn out, but you should have had a noticeable shake in the engine (miss). The exhaust leak should be easy to find with a stethescope or rubber hose held next to your ear-move the tube around and the closer you get to the leak- the louder it will sound in your ear. The defog/heat issue needs more info. Could be a charging issue if the added voltage draw is making the vehicle discharge if my understanding of your notes is accurate. If the charge voltage drops below 9v (needs 13.25-14.5v) the engine will cutout and die. Sounds like numerous problems and needs more investigation. Take it to a good Toyota shop cuz throwing more parts at it may be wasted money. Good Luck-- SB