If they care enough to give you estimated octane with a label maker, I'd say the station operator knows what's up and does indeed blend with 93. It's so unusual and specific I'd give benefit of the doubt.
I'll never be at that power level, but I know there are at least two other cars that have the next build up from mine (1200TQ rating) and have their engines being built now. I am not a forum sponsor, but I do make hardware and I have sponsorship involvement in those cars. I'll probably land...
The clamp is welded to the pipe, but the exhaust mid-pipe uses a slip fit onto the downpipe. It is not welded. Get a dead blow hammer. Pull harder. Use twisting. Use more force. It's gonna be stuck on there pretty good until you get the slightest bit of movement, at which point it'll pop loose...
Yup, these are all CAN codes, and those are the two wires the flex fuel kits ask you to modify in the passenger footwell. This is poor connectivity, loose connections, improper depin/repin, something like this. But it's all in the wiring.
It's not difficult at all. But just go flex. You're already doing most of the work with everything else. There's no reason to skip flex on this platform.
It's very easy to use. It just plugs into the OBD port. It scans for info over the port using OBD/CAN bus, so it's not really "specific" to any one car. I use a pair of Banks gauges on my own Supra.
It does mess things up if you don't make the tire thinner to compensate. Just by way of example, napkin math:
Let's say a 285/35 18" tire is OEM. If you wanted to go up to 19" wheel, you'd take the tire down to 285/30 because the one inch you gain in wheel diameter is offset the by one inch...
Just for total clarity: you do not need a big turbo or a built transmission for Stage 3. Some people just find it too aggressive and prefer to run Stage 2.