Fuel
 

How can you tell if the AFR is bad or going bad, My car runs in he lean all the time--The tail pipes never get dark color they stay a rusty color and my bumper has this flim from the exhaust, It runs great other then that but this has been doing it since i found the hiccup problem which was a plug. 3months now for sure and i think if it goes on i am going to melt down the engine..I don't drive city, all highway miles. I have change MAF and coils all new, plugs are correct heat range. I get about 23 to 25 mpg,
Thanks anyone for help.
Art,

PS: if it is the AFR how to do it.

Are you getting a check engine light code on the dash? You may have to check to see if the oxygen sensors are bad. Good sensors will communicate to the ECU to mix the air/fuel to the correct ratio

No light and no codes what so ever,

do you have an AFR meter? becauce that's the only way to know your running lean for sure. If you are you might want to look into your fuel delivery system. Check the pump, replace your fuel filter...a clogged fuel filter can really effect engine performance. If there is no codes then there is probably nothing wrong with the injectors. BUt checkn the fuel delivery system if your running lean. And if you haven't already buy an AFR meter.
Wish I could help more
~Jedz