Got mine from fleabay, topgaiters. Can't see a listing for it now, but it's decent enough for the job. There's a few others on there if GM's Cookbot tip doesn't come through.
The judder after traffic could just be heat build up and/or the slave on the wane so the clutch isn't operating optimally. Mine did that when I very first got it and culminated with the pedal sticking to the floor. When my flywheel was on it's last legs, I could feel something weird clunking/wobbling through the clutch pedal.
The rattle isn't the heat sheilds on the cats is it?
I'm confused, that bloke is on about power and torque, I was under the impression octane rating of fuel is all about delaying detonation under compression. This looks like bad science.
Upload can be quite slow (in my experience) if you have a lot to push up to the cloud, however if it's just one or two, it sounds like it's something else. This isn't El Capitan specific, but worth a run through.
http://www.gottabemobile.com/2015/06/02/how-to-fix-os-x-photo-syncing-problems/
Kinda with GMB above after fitting last year for the first time, ran Michelin Alpin PA4s, they're good but I just don't get on it when the weather sucks.
Got a full set fit in the garage for OEM RAYS, only done 5-6k. If you're after some, PM