i have a 94 lexus gs300 i failed emission because of high nox levels. i have done tune up,changed everything to do with egr valve.took intake off car and completly cleaned and everything back together correctly. Car runs better than ever but fails emissions everytime. Any suggestions

 

change all of your oxygen sensors...there are 3 of them

 

your car is running lean, any check engine lights or anything that would suggest its cutting back the fuel? either that or you have not CATs haha but i doubt that

 

There may be a stored error code even if the check engine light is not on. Try pulling the code to diagnose.