Just watched a tiny bit, what I saw is you're not using the full track width. You're getting close to the inside at the apex but trying toi hard to keep the car from sliding across the track and going off the outside. Also, check the power band on the BRZ. You want your shift points to be where peak torque begins to drop off.
For a good demonstration of the cornering technique, go try the Spa CE. You must take Eau Rouge, Radillon, and Blanchimont at full throttle. Don't try that just yet, familiarize yourself with the track. Or you can go run the 1 hour Spa race in the Gr 3 Porsche, you'll learn Spa real quick that way. Now start experimenting with Blanchimont. If you have the F1500 T/A or the MP 4/4, use it. Just after the penalty line and the first left, guide the car to the right so that your right hand tires are on the curb and throttle is wide open. When you enter the braking zone, cut your wheel HARD to the left, do NOT hit the brakes and do NOT let off the gas. The formula cars will corner on rails, showing you the correct line and speed. Now hop into the 911 RSR you used for the CE and do it again the same way. The first few times you will wind up in the grass. Keep trying til you nail it.
Now let's go back to College, the wide chicane roughly halfway through Spa. Ignore the line here. After the right hand turn, during the short straight, hug the outside curb. As soon as you get close to the left handed, cut HARD and punch it. This earns you an extra half second or so at full throttle towards Paul Friere. Don't brake too hard here, instead, move to the left, cut Paul Friere down to the inner curb, slip left again, cut Stavelot to the inner curb, then smash all the way to the chicane. Once you master this you'll be cutting 2:23.0 laps in the 911, or any Group 3 or tuned road car for that matter.
Now we go back to the beginning. At Eau Rouge you're faced with a left right left before the Kemmel straight. The 911 can enter Kemmel at 242 kph. Incidentally this same combo is mirrored on Sardegna Road A on the east side, and the same technique works there.
As you approach Eau Rouge, hug the right hand wall. Cut the wheel hard left and insert the car into Eau Rouge with your wheels on the left curb. Do not hit the brake. As soon as you enter this, cut hard right and keep the gas pedal flat. The car will slow down a bit and then pick right back up. You will appear to drive over a wide curb on the left side of Radillon. At Sardegna you do have to brake a bit after the initial right hander, but the braking time is microscopic. If you do it right it'll seem that you're about to hit the right hand guard rail. You may go onto the curb a bit. Mastering all three of these techniques will get you lap times in the 2:19 range, earning gold on the CE and confidence everywhere else.
On multiple S turns it's crucial that the slowest part is the first turn, then you build from there. As long as two of your tires are inside the line, you're in bounds. If the other two are on something dry and solid, you're good to go. You must enter each of the turns on the outside even if you have to sacrifice a bit of speed.
Anyway, go back to Spa for a while, run the race there, and take it flat from Le Source to Les Combes, then again from Stavelot to the chicane. Get used to thinking the car will fly off track. Get used to exactly how much you can push it, it's way more than you know.
The 911 RSR is good for this for its high grip, low top speed, and the fact it's used in the CE. Trust me, once you get this down, despite being a bit slow, that Porsche will pass everything but a gas station. If you want to pass that, switch to the e-tron, you'll pass everything but a wall socket.