94 Intrepid, losing power, gas mileage, tranny

I have a 94 Intrepid. It recently started getting bad gas mileage and losing power. When it idles, it kind of putts. When u go to take off, it boggs down, and then smokes the tires or takes off fast. It's backfiring at times. When it's cold, it takes a while 4 it to shift into gear. Someimes it won't shift out of 2nd, but if you turn the car off, it will reset, and run fine. Has a strange smell after u drive it for a while but all fluids are good. Sometimes smokelike vapor comes in the car up through the bottom of the console between the seats. Loses power going up hills and if you put ur foot into the gas it has no power. Used to have tons. Is there a sensor that could nake it run bad, or maybe the catallatic converter cause that? Thanks