This is a part of your car's emmissions control system, I would not have thought it would have effected driveability, but then it already has obviously, this may be something programmed into your OBD II system to encourage you to get it to a dealership and have it repaired too, its sort of an iffy situation, as to what is actually wrong, hard to say, could just be a sensor gone bad, could be something else, you may have to take it into a dealer or good independant garage, if you can find one that is willing to tackle it I would go for the independant, dealers are not your friend, especially once the warranty is expired.
