Thats the O2 sensor right on the exhaust manifold behind the rear driver side cylinder isnt it? Is there a way to test if the fuel mixture is correct if a check engine light isnt tripped? Also with the magnaflow cat and the Ubend delete theres no check engine light on like everyone has told me there would be, so i think the down stream O2 sensor might be shot. I ordered the simulator from 3800performance today so maybe that will help. I also use the air temp module slp has listed on their website, coudl that be causing it to run lean?

 

You can see the upstream o2 sensor sticking up out of the exhaust between the engine and firewall. If you have long skinny arms and nimble fingers you could remove and look at it. Mine was obviously fried. I'm not sure about your other questions. Maybe one of the more tech savvy members could help you out there.

 

Your catylic convertor is under warranty from GM until 120,000mi. They have been a real problem. You are luck you got that many miles out of yours. You might be able to get re-embursed for your repair. I did. Over $300! Check with your dealer.

http://www.cardomain.com/ride/2319272

 

Here is a quote from a reputable website:
An air temp module is simply a fancy packaged resistor made for people who don't know any better. Companies like SLP offer this for ~$25 and many are lured into purchase by its low price and ease of install. It tricks your PCM into thinking it's cold outside and therefore "optimizes timing". In reality it does little to nothing and cannot change commanded timing by more than 1 degree (and that's on a hot day where you probably can't use the extra 1 degree of timing anyway). Save your money and don't buy it. If your curiosity gets the best of you, buy an 8k resistor from Radio shack and save $24.50

As far as your rear O2 sensor goes...it is only used to make sure the cat is ok. It does nothing else but this. I have not had a cat or rear O2 in allthree 3800's i've owned. I threw a code in one and thats it. Its kinda hit or miss if your gonna throw a code or not. The Upstream O2 is the one that controls everything to do with fueling. Pretty sure if you look it up, O2 sensors start getting innaccurate readingsaround 50k and should be replaced around 75k at least.Just like plugs and wires...just because they cango a 100k+ doesn't mean you should. I wouldstart there first beforeanything.You already covered the fuel filter...maybe try the air filter also. Ican't remember what a dirty filter causesrich or lean i forgot. Actually if you haven't already please plugs and wires just because the way it sounds your not up on maintenance.
Sorry i'm probably a little overkill but here is what i do routinely: Wires every 50k, Front O2 every 50K, Autolitecopper plugs every 4K, mobil 1 Synth oil every 4k, mobil 1 4.3L filter (which is an inch longer((more Filtration))every 4K, Sea Foam in oil and gas tank every 4k, High flow fuel filter every 12K, Recharge air filter every 12K, PCV filter when i remember lol, Supercharger oil every 30k, and tranny drain (not flush) along with filter every 30k. I think that about covers it all...at least thats whati remember anyway.

 

I just purchased the vehicle approx 6 mo. ago so im unsure of the actual maintenance of the vehicle prior to my acquiring it. Being on a tight budget ive tried to replace what i can when i can afford it so it has recived new MSD wires, iridium plugs, a K&N drop in filter, premium oil change every 3000 miles, a tranny flush w/ filter, and usually around 93 octane w/ some type of cleaner. Ive since had the throttle position sensor tested with no problems. This weekend im having a diagnostic run on it since a friends father has one i can use for free. Along with the O2 sensor the MAF is also in question. Since it does have a high flow air filter and other relatively minor performance upgrades could it be the factory computer settings are no loger sufficient and need to be reprogrammed? Once i fix the problem how can i test the vehicle to ensure its no longer running lean?



...and my cat was only on a 87000 mile warranty... which sucks

 

Well I'm not sure how to test the O2 nor the MAF. I do know if you look it up there are certain voltage(i think) readings they are supposed to be putting off.Honestly just get that O2 out of there and replaced. I highly doubt its ever been done. As for the MAF sensor just clean it. Well actually just read these:

http://www.clubgp.com/newforum/tm.as...amp;s=#2694936

http://www.clubgp.com/newforum/tm.as...anguage=single

Clean it like this:

http://www.fordf150.net/howto/clean-...low-sensor.php