I have a '75 2.0 Djet...

Haynes manual, page 41, item 19....

Nice.... the figures show items 1-18. Everything in the illustration execpt the ONE item I wanna know about!@! #19!

Three hoses tie into the air intake.

I'm guessing a pneumatic deceleration valve? Looks like item 10 on page 40?

My car is 99% desmogged and I'm thinking this piece is doing nothing good for me. But before I go experimenting with how things behave differently when I plug this stuff off, please WARN me if I'm playing with anything important...

?

Ok, how about a photo...

If it says "USA only" I have to ask... Why?
PDV? What good is it? It's alsmost outta there. Somebody stop me.
Anyone? Bueller?

Yep, deceleration valve.

It's an emissions part -- from Paul B. Anders D-Jet site on Rennlist;

"Provides additional air to the engine during overrun to reduce emissions"

It can also help keep an engine that is somewhat out-of-tune from dying when you push the clutch in.

Some feel that it can help prolong the life of the vacuum-related bits in the MPS, as it keeps the manifold vacuum from being too high. I'm not sure I buy this explanation, but I figure it can't really hurt, and it just might help...

--DD