Can I add something else to the mix. As a part time thing, I have been collecting stacks of information about exhaust systems and their design.

One very interesting thing I came across is where some exhaust builders actually drilled small holes in the header pipe, to induce air to the exhaust flow.

The theory behind this has nothing to do with the catalytic converters, but actually to boost power output. The air, or rather O2 introduced into the header, would ignite some of the unburned fuel, and actually speed up exhaust flow. It also increased exhaust temperatures, and the hotter the exhaust gas, the faster if flows.

Some racers even go to the extend to wrap the headers with exhaust wrap, to maintain exhaust gas temperatures and flow, and this wrap actually works. The hole in the exhaust is just another way of doing something similar.

The way I understand it, the AIS will close at the right temperature, or high RPM. Has anyone tried running the motor with the AIS either on, all the time, or, the hole open, to see if it actually boost flow, and maybe increase high end RPM power output? It might just be worth while leaving it open.

I have no idea what the end result will be, or if it will be bad for the stock pipes, but on an aftermarket exhaust, it might be worth while trying it.