I was looking at these throttle bodies because I'm selling one and I noticed one has a plastic fitting for vacuum hoses the other doesn't.

If you cant see what I'm talking about , in the TB on the right in the pic its on the top right corner.

Why would this be? They both came off a s4 turbo engine

jdm vs usdm TB

Really so the one that has the plastic piece is usdm or jdm?

How would I go about using the one without the plastic piece, is it possible ? That's the one I was going to use.

This is what I found.

On US TII's the double throttle system has two purposes. The first is to prevent idiots romping on a cold engine by holding the upstream secondary throttles closed until the cooalnt gets to ~140degF. This is controlled by the thermovalve (attached to the thermowax) which is connected to the manifold by vac lines and a check valve. The second purpose to slow the opening of the upstream secondary throttles so they don't open too fast, which can cause a stumble at low rpm.

J-spec TB's don't have the first function, only the second, hence the simpler linkage and lack of vac lines and thermovalve. Mazda obviously trusted Japanese drivers more than US ones. Note that someone's pulled the thermowax off the J-spec TB.

the plastic bit is the thermovalve, on the usdm tb

So I guess ill be fine without it, just dont romp on it until the engine is warmed up.

I would surmise that most peoples double throttle system doesn't work.

The diaphragm inside the actuator is busted on mine, so i just removed all that ****.

+1. they get worn, and stuff stops working and the secondaries don't open.

curious does one has an Idle screw on it( the one with the plastic thermovalve on it)

If you mean on the top where it would be located on the NA TB then no, neither has an idle adjustment screw that I noticed.

Which leads me to ask, where is the idle adjusted on Turbo models.

air bypass screw is located on the BAC for turbo models

look at my weird S5 throttle body from long ago. When I bought it, all the screws/bolts/nuts seemed to be stuck, leading me to believe it was all stock. mechanical OMP with S5 TPS(s)