I have 96k on the Q7 and through a Malone Stg1 tune (both TCU & ECU) and all has been grand, aside from what I'm assuming a dirty intake offers with a delayed throttle input, but other than that all has been incredible. Yesterday morning, I noticed a strange shuddering of the transmission at any sustained speed over 45mph. I also drove on the interstate for 100 miles at 80mph and noticed the same. Looking at the "efficiency" screen in the center cluster, I could see my instant MPG changing from 30-34mpg while cruising to an abrupt drop, and felt through the shuddering, to 20-25mpg on a straight run of the interstate. That's what helped me determine it's a transmission issue and not a clogged intake or sorts. I had a transmission drain and fill with a new filter at 86k miles, along with the front, center and rear differentials serviced with new fluids at the same time. All has been good until yesterday. Do I need another drain and fill and some LSD additives or could it be a TCU reflash needed? I didn't have any codes on my basic OBD2 dongle with the torque app (all I had with me at the time). Any suggestions? I want to make sure it's ready for an August road trip of 4k miles and would rather not have to fix anything out of shop while on the trip for a couple weeks.

Here are the stats:
2015 Audi Q7 TDI Prestige with 96k miles
Malone Stage 1 Tune (DPF/SCR delete), with increased Oil Pressure and Left Foot Braking, Autobahn Stage 1 TCU Tune (3" Rawtek DPF/SCR Delete Pipes)
EGR is still in place, Swirl Valve is still there...