The chart is available at my website, which was mentioned in the thread, so it wasn't really necessary to register here to know it. And yes headers is huge improvement and it can be accounted for (they even make improvement with stock software). Even stock 1uz headers do.
No idea. Haven't personally driven one. I only build engine swap projects.
By the way, we are developing software that will enable IS250/300/350 etc 3UZ swaps retaining ABS/VSC/TRC as well as aircon and instrument panel operation
I highly recommend to use stock air filter at first (remove hood, etc)
When you will build your 1st ever custom intake, you WILL have problems with erratical MAF reading. So keep stock intake as reference point
Light flywheel is not something you want especially with a/t .