Done and dusted (hard difficulty... mostly)
Lake Louise - Nismo 400R '95 - I fitted this thing out with all manner of upgrades to get it to the suggested 600PP on snow tires. It was complete overkill. I created a monster. Easy win.
Grand Valley - Ferrari 308 GTB '75 - Upgraded this thing to the max PP. I finished in P2, just behind the Lambo. Usually I'd say that was good enough, but today I wanted to win this one. Went back for a second try and won it handily.
Watkins Glen - Hyundai Elantra N '23 -
@Famine's article suggested a PP of 600. I went a little higher than that -- with all of the sport- and club-level upgrades (IIRC). Made for an easy win.
Nurburgring - Lexus LF-LC GT VGT - Driving this car took a bit of getting used to, but even so, I had no problem catching the leader. Another easy win.
Autopolis - Mazda Atenza Gr.3 - I jumped in the race on RMs, thinking I could do a 6RM-4RS strategy. Midway through, the first lap, it looked like the fuel would easily last the whole race. I decided to bail and restart on RH tires, hoping to do a no-stop. Sadly, by lap 6, it was obvious the tires weren't going to last. I stopped for some RMs. I was only able to muster a P7, some ~30 seconds behind the leader. I figured I either needed to switch cars or drop the difficulty. I chose the latter. Down to 'normal' difficulty for the second full run. I ran the 6RH-4RM strategy. It was still a challenge in this car. I only caught the leader towards the end of the final lap. Another win. I'll take it.
I won a Ferrari VGT for the car ticket.