I figured out the issue, so hopefully this will help others in the future. I won't go through the long list of things that I tried, but I found the root cause to be the fact that when I had converted from the stock tune to the DSP5 tune, it had switched the units of the "BASE TORQUE" table in ALL 4 DSP tunes to "Nm" instead of "FT*Lbs". When I then copy and pasted the values that I wanted for the base torque table from a modified single tune those values were in "FT*Lbs" but the DSP tables that I was pasting into were set to "Nm".
This was responsible for a heavy defuel in all 4 DSP tunes. The "BASE Torque" tables in the base tune were still in the correct "Ft*Lbs" units which was why it shifted fine in the Base Tune. The units were Imperial on all other tables EXCEPT base torque which was set to Nm after converting to DSP5.
Hope this helps someone in the future.