My CEL on my 95 3.8 LX comes on intermittently while driving, then goes back off. This has been happening for several years. At first, I got all kinds of crazy codes, so I replaced the MAF and the problem went away for about a year. Then it started happening again (the codes were all fuel trim related) so I replaced the oxygen sensors, and it happened less frequently. The codes I am currently getting are 172 and 181 (HEGOs stuck lean banks 1 and 2) and 176/189 (adaptive fuel limit rich reached banks 1 and 2). I don't think it is HEGOs since they are less than a year old and BOTH sides are showing the same problem. I have checked the MAF and TPS, both are good, and I have also cleaned the throttle body, decarboned the intake, and replaced the lower intake gaskets, no effect. Also good fuel pressure, newer fuel filter and no vacuum leaks. The car runs great, except for pretty poor gas mileage (15-20 vs upper 20's a few years ago). My 90 SC which I drive hard gets better mileage. I run premium gas and have tried several different brands. Any ideas? I can't think of anything else to check, every test procedure in the ford service manual for these codes has checked out ok, and I can't think of what else to look for.