i have got my car taken to so many shops and i have been told so many times i am running too lean causing me to run high in NOX,i know that i am running lean but no one has really told me the cause of it or how to fix this running lean problem..? am i not giving enoug gas,sparks,or air? what do they mean by me running lean and what do i need to do to stop running lean..? my nox is around 2000 at 15 and 1900mph at 25mph. my CO and HC are fine the results they showed were cut in half from being a gross polluter.. so i just need to know if i need to change fuel injectors, fuel rail, throttle, for me to stopp running lean..? and i was told i might have a vacume leak so i had replaced the hoses and put clamps for nomore leaks, but still idle goes down..

 

To check for vacuum leaks get a bottle of carb cleaner and spray at areas around your engine bay with engine running. If your engine bogs then you found your leak.

What mods do you have? intake exhaust anything that would add air?
Any cel's

One thing you could do to raise fuel is get an adjustable fuel pressure regulator and a fuel guage. Add about 5 psi or so to get your afr's right.

Get someone with a wideband to plug up to your exhaust to see what ratios you are actually running.