Newbie with a sensor ?

Howdy all. Looks like a decent site. A friend directed me here form jeephorizons. I'm stumped on a problem with a '91 XJ sport, 4wd, sport, manual. It has almost 300k and was running like a top until I took it in for a high-flow cat and flowmaster exhaust. As soon as the shop lowered it from the lift it wouldn't start. After much coaxing and holding the pedal to the floor she sputtered and caught and I managaed to get it home as long as I kept the revs tween say 1500 and 3000rom. If I let it fall below she stalled and if I floored it she bogged and sputtered. but in this exact rpm range+/- she ran like a banshee. So I know the exhaust isn't the issue I thought backpressure maybe being as she never had a perf. exh b4. But no plenty of air out back, but the cat gets hot and turns colors and I think too much fuel is being dumped. I have replaced the TPS, the IAC motor and put on a bigger bore TB with a spacer. She has new wires, plugs, cap and rotor and fuel filter. Not fouling plugs. The thing is to get it to even catch I have to hold down the gas to the floor and choke off the intake. After awhile she will catch, rev and settle down to a decent idle. SOOO..... I know the new IAC is working maybe the TPS as well. I removed the batt to reset the puter as well as ran it at 45 mph someone said for 10 minutes or so. But I am still having problems with it bogging over 3000 or so if I floor it and if I don't feather the gas pedal it will cut off. My thoughts are before I replace the injectors to make sure it's not the maf or mat or map sensor whichever these have? The point being as I can choke off the air intake and only allow a little bit to pass thru and it catches and starts....this with holding the gas down and then pumping it. So anyone think this is a fuel/air issue or any other ideas? Any help would greatly be appreciated as she tells me she is tired of sittin around and wants to hit the trails..haha Thanks.

O2 x2 make sure the exhaust shop didnt burn or unplug the wires...just unplug it and see what happens

check and see if they booged the O2 sensor wires when they were installing the new exhaust.
Why did you leave the shop? If it ran fine going in and didn't run after it came off the lift...

Changed the o2 sensor. And it runs the same with it in or out, just louder with it out haha. Swapped it with a OE bosch model so don't see where that would be the prob. SO nobody agrees with the maf sensor eh? hmmm And I left the shop because what was I gonna do sue them? haha It was a mom and pop shop and they did what I asked them to do, throw an exhaust on it, wasn't their fault the jeep threw a fit after changing it. Not like I coulda asked them to put it back on and besides it wasn't a exh issue therefore not their fault therefore why not leave. I think it was typical on my jeep, when something decides to go it don't matter where u r or what u r doing...haha But thanks anyways guys.

O2 sensor does not come into play until the engine has warmed -- even then....

I'm not sure about this, but I think I've read of similar problems as a result of a plugged cat. Maybe, your hi-flow cat is a no-flow cat.

That's what I thought at first but nah she's throwin plenty of air out back so it's not plugged. However after I do get it to run somewhat the cat gets turns red, so that's what makes me think that too much fuel is being dumped and burning off in the cat. Who knows maybe the throttle position sensor didn't take or my computer is screwed.

disconnect the exhaust to test to see if the cat is clogged just a suggestion, also when they installed the exhaust was the vehicle grounded maybe the computer was fried from welding another suggestion hope these might help

did you check the resistance on the coolant temp sensor and the manifold air temp sensor? check the voltage on the map sensor and make sure it holds vacuum?

Yeah Brian, not the cat like I said it's pushin alot of air back at the tail pipe and if the computer was fried wouldn't it have fried the whole thing and not just like one or 2 things? Nice idea though never thought about the welding and grounding issue. Hippy I really like where that came from because it's new and haven't tried those yet...haha Can you please advise on how to test the resistance and that vacuum leak? I don't hear any hiising but if the map or maf sensor isn't getting any vacuum to run properly how would I even know that? When I put on the 3in. lift kit I did change the front bumper and messed with that vacuum ball up front, maybe this got disconnected? Also where is the coolant temp sensor and manifold air temp sensor located? I think the maf or map whichever is the one mounted high on the drivers side firewall correct. Thanks again guys.

HEY GUYS, heard something about a map sensor modifier since I installed perf parts I need to get my fuel curve back in line.....This sound like a plan for my prob anyone? haha Also has anyone done one and how easy/hard was it to install? And what are the benefits/drawbacks on these things....anyone? Thanks!