Any all exhaust leaks (fore and aft of the O2 sensor) and or having the o2 sensor too close to the end of the exhaust pipe will cause the AFR gauge to read false lean @WOT
high rpm WOT leanout ='s lack of fuel system flow volume.
For a high performance application using the 600cfm eddy carb start with this calibration
.098" pri jet .068x.047 pri rod .101" sec jet. 4" to 6" piston strep spring.
5psi fuel press at idle. not less than 3psi @WOT high rpm.
Your narrow band O2 should stay pegged at .800 to .850 V @WOT.
you got a leak in the exhaust system. or the ignition system is misfireing or both.
or your fuel pump, fuel lines, in tank pick up tube or fuel filter is fubared
Last edited by F-BIRD'88; 07-01-2012 at 03:34 PM.