Well, got the car tuned. If you didn't see my last thread: 5.4L MMR block, t-56, kooks headers, o/r x pipe, magnaflow magnapacks, procharger kit ~ 6-8 psi (not sure yet). Car was getting less than 3 mpg. Can you say RICH??? Took the car to the shop. No vacuum leaks, but turns out the PO tried to tune the car himself. Did it with an SCT tuner i guess. So, I got the car tuned with a Diablo tuner and now its getting 20 mpg, but still running rich. Pulled the Service Engine Soon light's codes. I believe P2196, 0132?, 0173?, 0152? All rough guesses because i don't remember, but they all were O2 sensor codes. So the car had 4 o2 sensors stock right? due to the headers and exhaust, there are only 2 now. So what should I do? The shop told me a wideband controller would be good and that AEM's is one of the easier to install, reliable ones to go with. Or should i have an exhaust shop drill and tap holes and install 2 more o2 sensors? I don't know what to do! In the mean time, fuel is still washing carbon down the cylinder walls, blackening and contaminating my oil. I bought oil change stuff, but whats the point of changing the oil if it just goes black again? I NEED to get the 02 sensor thing figured out!