Running crazy lean intermittently

[one_boosted_si]

Car specs:

B16 w/ built bottom end (rods and pistons)
Vortech @ 13-14 psi
RC 550's with Walbro 255
S300 obviously
hacked up calibration by me that I downloaded from here and got car running
Self socketed P28

Background:

Been running this "tune" for a while but have had problems with it for a while. When running at higher RPM and cruise/very light throttle my wideband will jump from normal (13.5-16.0) to uber lean (16.0-18.0) and hover there. When this happens the vehicle feels strained and more throttle has to be applied to keep at same speed. You can add more throttle at a heavier load/boost and the mixture will jump to 12.5-13.5 but when returned to light throttle/cruise it will jump back to uber lean.

At first I thought that it might be that the ECM is adjusting a/f ratio for emissions but it's not a "timed" event that seems to have any schedule.

When the vehicle jumps back to normal it seems to spring forward from the unneeded extra fuel/load input. The concern seems to get worse at the vehicle speed is increased/higher RPM range.

I've attached a datalog to help diagnose, thanks for any help in advance and I'll try and check this frequently for any additional info that might be needed. The datalog is from operating temperature at idle to varying vehicle speeds with light cruise throttle.

Thanks!

Ryan

[one_boosted_si]

nothing from the far reaches of tuner land? Any help would be appreciated!