The only VSS I have is on the trans output shaft and mine shifts the same regardless of TC gear.
Ther'es a few things you can do in the lean cruise area to get it to stay in V4 mode longer.
Raise your TPS max% - I believe GM set it at 6%, raise it to 20%.
Raise your TPS HYST - I believe GM set it at .5%, raise it to 3%
Then you can change your enable/disable vacuum thresholds to suit.
I'm not getting 28 mpg, but I'm getting better than you are with my 6,000lb Jeep Wrangler. Conversion is still too new and I only have freeway data while pulling my camper trailer and I was getting around 14 mpg @ 75 mph. I would assume without that bigger brick back there it would be higher than 14...? My Edge controller says I'm getting around 22-26 mpg through town. I didn't have it with me on my trip to Moab last month to know how accurate it is...