Running too lean?

Skull Crusher

Carbon deposits. You can't tell from your exhaust tips if it's to lean. Carbon is the black residue left over from the burnt fuel. With 10-15% ethanol used in most fuel today, it leaves a black carbon residue which is collected at the exhaust tip or exit. Every automobile today will have this residue.

You need to run a spark plug chop test and actually look at the base of the spark plug insulator with a magnifying glass. If it's really dark brown or black you're running rich. If it's really light tan, light gray or chalky white you're lean. What you're looking for is; a medium to dark tan. You can install a A/F Gauge but it's readings are more relative to the climatic conditions.

If your running an intake, headers, test pipes or HFC's, cat back and improved intake manifold you might be a tad lean, possibly. If not, there's no way the ECU will allow a lean condition.

Another way to tell is to pick a specific gear 2nd-4th, hold a specific RPM at around 3700-4000 and see if the Z surges slightly. You'll know exactly what I mean if you feel it. If it does, then it could be an indicator of running lean. You will also develop a lean "POP" under deceleration in every gear but will be progressively louder under higher rpm load in lower gears.