2017 Silverado On3 Turbo - RPM bobble in first gear

Trying to help my friend with his 2017 Silverado fitted with an On3 turbo kit. I thought we had the street tune pretty well sorted out on 12 psi boost, but at the track we data logged a stubborn RPM "bobble" in first gear. Somewhere between 4,100 to 5,100 RPM (depending on how much boost he leaves on) the RPM takes a brief 600 to 800 drop. I do not see any change in ignition timing, injector pulse, throttle position, torque management advance - but yet there is a 600 to 800 RPM drop during first gear launching from a stop. I would love it if anyone cares to take a look at the attached log from a dragstrip pull (note the RPM drop at time 31.780 sec). This truck runs in the 7.7 to 7.8 second range in the 1/8th with lots of promise for better ET if we could get a clean pull. I should probably ease back on shift TM to help with the RPM recovery after shifts. The tight converter is dropping over 2,000 rpm on shifts.

Any suggestions on the attached tune would also be welcome. The truck put down 550 rwhp - stock 5.3 with just the On3 turbo kit around 12 psi if I remember correctly.Attachment 83004Attachment 83005

Try logging TCC slip and calculated gear ratio... Can also log anything related to trans input and output speeds. Something looks to be slipping...

Yes I tried the tune and uploaded it then data logged it. about the 4000 the trans acts up like the engine is working but trans is delaying the power. I was running just the spring pressure. On my 5.3 2wd on3 turbo truck.
what size turbo? I have a new turbo this week, different controller setup, and then we will dyno tune it.
What exhaust do you have? also what O2 are seeing at idle and wot?

Stock SOI table along with 7.5-8.5ms pulsewidth.....not good