Well, as you can tell the main 2.25" is pretty darn old and will be replaced when I go to the twin carbs and extractors (what you call long-primary headers).
It's on a stock 225 at present - only changes are the 2.25" pipe from the stock exhaust manifold, and a performance air cleaner.
I picked up the Y-pipe and butterfly valve (+cable and dashboard switch) from Summit. The price including delivery to Australia was still cheaper than the same product from a retailer here.
i am impressed with the quality of the QTP assembly. It is completely serviceable and each individual part can be replaced. Much better than some of the cheaper ones where the cable is solid mounted to the valve and the electric motor is integral to the valve . . .