transmission issue troubleshooting

[uhlhazard]

Hello I started doing tuning just a few weeks back. I'm realizing the learning curve especially with my 94 4.3 cpi engine/code and sticking with the stock chip just datalogging for now.

Anyways yesterday I noticed some odd transmission behavior. Light throttle in 3rd at 25-30mph the trans jumps back into 2. Seems like if you give it a little fuel it shifts gears really quickly. I went around the block and made the attached xdl. Anyone familiar with this issue? I checked the trans fluid and it was at the top of the cold mark @ 190* fluid temp. I have a deep sump pan/filter from a late model 4l60e so I'm doubting this is due to a low fluid condition despite it being slightly low.

I recently had a code 42 "Ignition Error" blink the service engine soon light on and off so I'm hoping I can blame the distributor and be on my way. Can anyone make heads or tails of my datalog?

This is all on a 1994 GMC T15 Jimmy with a 4.3 Vortec/4l60e