I think I need a new injector or two and I would like to know how to find out witch ones are problematic. It runs great! but smokes gray at an idle and smells rich when ideling. I have 205,000 MI on it and the injectors were replaced at the dealer at 99,000 MI So I called GM last summer and let them know at 199,000 it needed some more injector they told me it had been in service past the 7 year point and would.nt pay to fix . so I am a Mech and can change the injectors my self but I need to only replace the bad ones or bank at a time as It is more than I can afford at one time I am afraid. I did see a internet ad for Get real Diesel that advertized $125 extchange on rebuilt Injectors and $999 if you send them yours and they will send them back to you in 15 days I think . Any thoughts ?