I don't have a pic of my old o2 before I replaced it with this denso, but it was crusted in black soot. Now with these new muffler tips, if I drive more than 20 miles, I start getting carbon build up on the chrome tips. It'* so annoying. I have to clean them every day. If I floor it, I can drive less than 5 miles and have a darkening layer of soot, enough to make your finger black on a full circle inside one of the exhaust outlet. I mean I felt like my gas mileage has been improving with my lighter foot, but I still don't get more than 23 mpg. I figured it was because of all of my city driving.

Think I'm running rich? Or think I should wait for the aeroforce to tell?

Your aeroforce wont tell you if your running rich. You need a wide band O2 for that. I belive you can get a sensor and hook it up to your aeroforce though.

air-fuel ratio won't tip off to me running rich?

AFR, yes, that will tell you if your rich or lean. BUT, only a wide band O2 will tell you that. The cheep ones that run off your O2 sensor are basicly worthless. Mine has it'* own sensor, had to have a bung installed. There not cheep, $299 or so.

Some local shops have them and will put a bung in, test for you, and then plug it.

If you're running rich, it'* because of the O2. And it THINKS you're running good, so putting a gauge on it tells you nothing.

Now that I think about it, it makes sense. I can't explain my theory that'* in my head, but it'* there with a logical map and everything lol. Maybe if I see a junk o2 at a JY locally I'll pick it up for kicks and giggles and see what it does.

Gas mileage doesn't seem to be TOO horrible... but like I said it'* all city driving. We'll know this summer when I once again take the 600 mile trip to and from MI on the turnpike. Will also be driving about 1500 miles while I'm up there for the week and a half (did last year anyhow).

How old is yoru O2 sensor? Has it ever been changed? I changed mine a few months back and I gained about 2 on average and about 4 on hwy. Rockauto has them for abotu $45 or so. Changing them is not to hard and worth the effort. Changing a junk one wont tell you much, you have no way of knowing if it'* any good. Go with a Denso, dont use Bosh. You only need to change yoru front one, don't worry about the rear one.

Yep, I mentioned I replaced it first sentence. I replaced it with the denso off of rockauto.com. But, I have heard of o2s being faulty out of the box.

Sorry I missed that. Ya, I've heard that as well. the best way to find out if have a wideband test done. Tunners shoudl have this.

Ahhh I'm just not into putting that much money into getting that kind of thing done . In the long range, it will save me gas. I'll try to hit up the warranty at the dealer and make them fix it. They keep trying to charge me diagnostic charges for something thats covered under warranty. Go figure, 4 transmissions and I've not seen a penny'* worth on a bill, go in to have a simple shudder diagnosed and they want $60.

Before my trip this summer, I think I'm going to go in and raise hell. I'll offer to pay diag if its not under warranty, but I have full powertrain+accessory warranty so it should be.