I have a 99 intrepid with a 3.2v6 she is running rough and backfiring with po175-po172 codes, I have changed the mass air flow sensor and the plugs, no good. Here is the strange thing if I pull the ingector/coil fuse and put it back she runs great for a bit then back to rough.
Also I have no heat in the car I don't know if they could be related.
The codes indicate running rich on both banks. With that and the rough running, first guess is that the timing belt has slipped - ESPECIALLY if it is the original factory belt. I would suggest not running it until you determine that, because if the timing belt slips more or breaks (again, especially if never been changed), there will likely be expensive engine damage resulting.
agree with peva...on the 3.2/3.5 when the water pump starts to leak it gets hidden pretty well inside the timing cover...water pump leaks causing the belt to jump or slip..the hydraulic tensioner can be re-used if you SLOWLY compress in a vice then use a small pin (nail) lined up in the holes...are you able to get a vacuum reading? 17-21 in. is about a normal range...keep us posted I could give you a few more things to check