I recently posted a thread on how I replaced the radiator and cleaned out the MAF sensor and installed a new filter. I was driving and unaware of the MAF sensor being disconnected. I had a code and I thought I was having an electrical issue with my fans. The car was driving fine and I drove for about a week like that. The car was even running really cool due to the fans always being on. I noticed I was getting an average of 19-21mpg. I even made a trip to Las Vegas, a 4 hour drive doing 80+mph. Once I found the MAF sensor disconnected, I corrected the issue and the code was gone. I drove the car for about another week and I noticed my gas mileage went back to a crappy 16-18mpg, and I usually get a smell of unburned gasoline out of the exhaust. So was my car running lean the entire time when the MAF was disconnected or do our cars run really rich? I have a wideband oxygen sensor connected on my turbocharged Nissan and I would like to connect it to the Impala just to see how it runs. So am I better off running the MAF sensor? Or would I run dangerously lean? Please let me know what you guys think.