Hi all, I've got a 2002 Grand Prix Coupe. It has about 155K miles and is mostly stock. I've had the Cat replaced with an "OEM equivalent" and different O2 sensors trying to get rid of a recurring engine code. I've been driving it for 70K miles now with that code and no changes in anything except fuel mileage. Before, I got around 29-30 mpg and since the code started, it's dropped to about 21 mpg. I'm hoping to find some tips to getting those valuable mpgs back from this site.
I've done various things like a drop-in K&N air filter, different plugs, 2 different types of O2 sensors, cleaning the MAF twice, switching back to a disposable air filter and all have had zero affect.
