Wow, this turned into a useless flame-fest......

Anyway, I happen to agree with Rotarygod. I swapped over to an s5 intake manifold because I had one laying around and was bored. I was pleasantly surprised that the power was about the same (maybe a bit more?), but the power band kept on going for about another 1000 RPM. I regularly run my streetported s4 motor to 8k, when it ran out above 7k with the s4 intake. I'd say that constitutes a power gain.

Now, about implementing it, I recommend against using the s4 lower intake manifold. There are two arguments for using the s4 lower: keep the stock aux port activation, and it flows better. On the first count, the stock system sucks and won't work right with an aftermarket exhaust. On the second count, it is debatable whether it is actually better. I have seen both. I have actually used both, and couldn't really tell a difference. So here is the reason not to do it: it is a HUGE MASSIVE PAIN IN THE ASS. It requires a whole lot of grinding to make a new hole for the mounting stud that is in a different place on the s4 lower. And even if you do this without drilling a hole in the manifold, which is a very real possibility, then you still have to figure out how to get the nut on. Due to the tightness of the area behind the manifold, this is nearly impossible.
Also, the rod bending is a pain. I still haven't gotten it right, so I just premix.

So here's the synopsis: use the whole s5 intake with s4 TB. I would also recommend using RPM switches with solenoids getting air from the air pump. It is true that I wrote the directions on how to do it with lumbar pumps, but it is much simpler and cheaper to do it with the stock air pump.

That's a first lol