Too Lean?
 

Is There Any Easy Way To Check For Leaness? How Do You Go About It?

Re: Too Lean?
 

A PROPER plug read,
Determining whether you have a WOT fuel pressure drop off.
Listening by ear as you manipulate the sticks under power, and feeling for the "softening" of the motor.

Re: Too Lean?
 

Is reading the plugs considered as accurate as an o2 sensor reading on a dyno? I ask because I just built a 540 and on the last dyno run, at 3700-3800 the 02 sensor was at 15.1 which is scary to me, but we read #6 plug, after a fresh instal, and it was a nice tan. should I trust the plug or the o2 sensor?

Re: Too Lean?
 

I would think you should take more plug readings than just #6 if you are concerned about the accuracy of the O2 sensor. #2 and #7 are generally the leanest.