Help With 2 step Tuning hp tuners E38 with t56

I have a 240sx with an E38 ecm with cammed 6.0 with t56. Just added a turbo and bigger injectors(SEP1000 Long). Got the car running pretty decent but had some questions setting up my 2 step. Im using an msd 2 step box with a switch. i currently have it set to 4300rpm but when i use it im running very lean(about 1.20lambda) I did made a tune that bumped up the fueling in the areas under the 2 step but it kinda effect my regular/aggressive driving by making it too rich. any suggestions? I'll try to upload tunes and logs, one tune with the added fuel and the other with my regular map that runs lean on 2 step. I have a log with the fuel bumped but not with the regular tune yet I can make one tomorrow.

I jus made a few adjustments to the fueling and the timing at 4200 rpm on my most recent tune. going to test tomorrow but please advise on any other adjustments or ways of going about the 2 step tune as im not sure if this will effect drivability under heavy load conditions

Regarding your measured lambda. The sensor is measuring the oxygen content, if your MSD box is cutting ignition then the oxygen that would have been typically consumed as part of the combustion process will flow out the exhaust causing a 'lean' reading

Scott is spot on. Just in case it helps make sense of this, your lambda sensor is reading an average of multiple cylinders, and that average doesn't necessarily match the air/fuel ratio in any of the cylinders.

If one bank of your v8 had 2 injectors with different flow rate than the other 2, you could have 2 cylinders operating at 15:1, 2 operating at 11:1 and the wideband would read the average of 13:1, but it doesn't mean all 4 are running 13:1, in fact none of them are.

When using the 2 step, you're averaging fresh air from cylinders that are being cut by the 2 step, with cylinders that are operating normally, so the average will always appear leaner than the air/fuel ratio cylinders not being cut are operating at.