Hello Guys, I apologize about my broke English but I'm from south america and need a help, I'm turning crazy having an 500whp evo than I can't drive, lets see if some one can help me. After have tuned the cars pulls 514 awhp, so few day after that cars run ok when its warm but gets more time driving and hotter idler start getting lean about 16 to 17, only on idler above 3k rmp drive used to drive ok, but know my car afr change all the time, could be 13.5 on idler for 5 min, or maybe have a day and just changed to 16afr while driving, also when drive easy lets say at 3,500 rpm and get on gas a little quick the afr goes to 10 and the car fail, in conclusion what sensor or parts makes the afr change all the time??