Here's a short list of what Roger and I usually have between us.
Basic tool kit plus a small bag of more specific tools I like to have on hand.
Shark Tuner for those of us who are modded.
Breaker bar with 27mm socket (crank pully)
Battery impact gun
IR Temp gun
8mm/10mm nut drivers
https://www.amazon.com/Crescent-CTK170C ... B00F4AVRGW
Low Profile jack
https://www.harborfreight.com/15-ton-al ... 64545.html
Spare parts usually include:
Spare LH computer
Tire plug kit
Upper/lower Rad hoses
It's amazing how many times we've had to use each of these things on a trip with a bunch of 928'ers. One year on the way to 3rd Coast we had a GTS blow an upper rad hose at 165mph. Showered my car with coolant while I was behind him. We didn't have any hoses but we found an aluminum can on the side of the road, cut it to fit around the split on the upper rad hose, hose clamped it in place and covered the entire set up with silicone tape and it worked flawlessly for about 300 miles.
We forgot a tire plug kit and I got a flat out in the boonies, that sucked.
Hans had his crank pulley come off one afternoon and I didn't have my breaker bar or 27mm with me, but drove back to the town we just passed and happened upon a Snap-on truck which had one so I got an extra set up now.
You can never have everything with you that can go wrong, but with a little prep it can make it easier.