I have driven my car about 9,000 miles and the exhaust tips are barely dirty. Most g35 or 350z exhaust tips i see are completly black. Ive heard it can be real hard on your engine if it runs lean and was wondering if this is a sign. Thanks for any input....o, i don't clean the exhaust tips

 

dyno it.

 

No 350Z will have the same air:fuel ratio throughout the entire rpm range. The best test is wide-band monitoring. A car that runs lean will usually run lean near redline (LOP or lean of peak). Sometimes it will feel like the engine is starving. If run extremely lean, the combustion chambers will heat up significantly.

 

even if you run lean you sill produce hydro carbons, i doubt your not having carbon buildup becuase your running lean. You would notice a lack of some performance.