The A/F meter should be hooked to it's own sensor as per instructions .

If it's hooked to the same O2 as the computer, this may be causing a problem.


Check the fuel pressure if in doubt. The pump, filter, and FPR can cause problems.

High RPM power loss can be the first sign of a CAT problem, IMRC will manifest itself around 3800 rpm.

Is the rear O2 as new as the front?



"Those who cannot remember the past are condemned to repeat it" -George Santayana