hego sensor...?

when i first bought my xj, there was a dynomax super turbo muffler installed, very very badly at that. nasty welds and clamps everywhere. and the hego sensor bung wasnt in the tailpipe they used so they just left it hang there, i never had a problem, until a week or two later when the CEL came on... my gas mileage is REALLY bad.... then my tailpipe snapped at one of the crappy welds on the muffler when i was wheelin one day. so now im left with a muffler with no outlet pipe, and a dangling HEGO sensor.... and my gas milegage is even worse.... would any of these exhuast problems cause my MPG to drop severly like this? i use auto-lite plugs, and they are gapped perfect, i checked them and they are clean, brand new q-state synth blend 4x4 oil w/ bosch filter, brand new antifreeze, brand new fram air filter, brand new alternator, cap, rotor, 7mm wires and mileage is garbage... and i even have a ax15, u think it would help lol.... to get to my point, is it my exhaust problems causing the bad mileage or is it something else that i should check? if its exhaust, what set-up do you guys recommend using? thanks alot for the help....

certainly could. All those sensors are used by the ECU to get the proper fuel mixture. If it's in an open loop or limp home mode then it would be all screwed up

ok, well it onyl gave me one code which is good, it was the PO132 i believe? high voltage on sensor 2, which pretty much pin points it to the hego, i guess my only option is to fix it lol