If it were me, I'd do the hardware first and experience the difference. The decision to flash o change the ECU would then be an easier one to make, perhaps..?
I think this may be the scientific way. I could pick the exhaust up at the factory (date will be announced for splinter group and wider info), and then pop back and have the flash done at the factory later. If that's OK with them.
I must admit I'm quite excited by the prospect of shiny shiny, and a new task...………..
