The only reason I am mentioning this is because I would like to see a good battle at Monza, even if I finish last, I just want to have to fight for it.
It's usually best to use a higher gear for turns and keep RPM's down a little, it will reduce tire spin on exit without hurting lap time and also if you use a lower gear the car will always lose apex speed. There are corners that I downshift for where the car is close to the rev limiter, with the physics being the way they are in GTS it helps keep the front of the car planted if for example you use 2nd instead of 3rd for a corner where either will work but it usually comes at the cost of apex speed. There are decreasing radius corners that require it though, like that right hand turn on St. Croix right before that long, long straight. In that corner I lift off the accelerator, tap the brake to set the car up for the turn, then coast thru the turn while downshifting just before the apex, I think pretty much everyone drives that turn the same. At Lesmos the RSR hits the limiter in 3rd right at the lift point for Lesmo 1, I tap the brakes and coast thru in 3rd gear, I can easily downshift to 2nd but it will cost me lap time. Lesmo 2 I only downshift to 2nd when in traffic because the traffic usually slows you down a little but I usually upshift before getting back on the accelerator to prevent tire spin and a date with the wall. If you go to arcade Time Trial it shows the stop watch on your hud, blue for faster, red for slower than previous laps. Run some TT laps and keep an eye on that stopwatch to see what the best gear choice is thru the Lesmos. Even though TT lap times do not align with lobby times very well you can still get an idea of the fast way around the track.