[beepbeep]

Intake setup on picture was created by small shop that is specialized in custom intake/intercooler design, not by me. They also did all the calculations.

Generally, you don't want air to make sharp 90-degree bends. Intake pic posted by Red9 will work but isn't optimal.

Don't get me wrong, ITB probably do provide some improvement in throttle-responce but IMHO those gains just aren't worth the fuss in most street applications. Not even 997 Turbo uses ITB's, but they went extra length and fitted VNT turbochargers (avantgarde technology) to cure turbo lag. Don't you think they would also use ITB's (old & prooven technology) if it could also help?

My personal opinion is that ITB's (and their supposedly better throttle responce) are grossly overrated. We did some calculations on this. We have twin plenums with roughly 3L volume each. 3.6L engine turning @ 3000 RPM will gulp whatever air is trapped between the throttle plate and valves in such a short time that fitting expensive, finicky and hard to adjust ITB mechanism just wasn't worth it. There is also added problem of obtaining quality pressure signal for variety of sensors and devices and crossover pipe (to equalize pressure differencies between turbochargers).

In our case, there are following devices that need pressure signal:

1. MAP sensor (needs even vacuum signal, doesn't need flow)
2. Twin BOV's, quite huge (need vacuum signal and usually flow a little, when pistons start leaking).
3. Bleed solenoid valve ragulating pressure to wastegates (needs vacuum and will induce airflow when it starts bleeding air)

Obtaining all this from a stack of ITB's is a maze of pipes, reservoirs etc. It also raises the chance of one of those pipes rupturing.

It only takes one simple ruptured hose going to MAP to fool ECU into believeing that boost is much lower than it actually is = piston meltdown in matter of seconds when you run 1.4 bar.

Factory team can afford technicians and materials that will make all this reliable, but for semi-professional team the riskts are too high compared to gains.

We connected all signal lines to billet block on crossover-pipe, just to be sure that no crack/leak would ruin the engine. MAP bolted directly to the block so there are no hoses going to it at all.

Good throttle response on turbocharged engine can be obtained by fitting ALS (Anti Lag System) and careful sizing of turbochargers and runner lenghts.

I suppose fitting ITB's is somewhat easier on turbocharged engine that uses Alpha-N + MAP in blended fashion (where pressure signal is obtained from turbocharger north of throttle plate) or Mass Air Sensor.

For N/A engine, no problem. Just fit ITB's with Alpha-N EFI and you are set.