There are so many electronics on those cars, it could take a while to pinpoint anything. as for the thumping in the rear, maybe check the wheel bearings, they maybe sloppy.
O2 sensors could cause the fuel trouble, idle air control vavle. a number of things,
I personally had issues for months on a 95 Ford Ranger, I replaced speed sensors, O2 sensors, antilock brake sensor, fuel filter, plugs and wires, all trying to solve code problems on the check engine light, turns out, one day the alternator started knocking, so naturally I replaced it, and BAM, all problems were gone. Everything was getting low voltage cause the alternator wasn't keeping up with the demands.
good luck, maybe someone else will come along and have some more insight on the fuel troubles, there are a few auto techs here.