[Dave at Pelican Parts]

Required? That depends...

The engine will run without it. The only time you'll ever notice the lack is while you are decelerating with the throttle closed. The engine will probably burble and pop a bit without it. Also, when you are at medium or higher RPMs and then push the clutch in and let off the throttle completely, the decel valve can help keep the RPMs from dropping far enough for the engine to stall.

Early 1.7s did not have a DV.

I would install one, but I'm a believer in the EFI system.

It may or may not be required by your local smog laws. Even if required, it is unlikely that a tech will notice its lack.

I don't have a part number handy, but I'm sure Pelican can supply you with one if they're still being made.

It mounts to the upper bolt that also holds the Manifold Pressure Sensor bracket onto the right side of the engine bay. It has three vacuum hoses, two fat and one skinny. One of the fat ones and the skinny one both get hooked up to the manifold. The other fat hose gets hooked to the air cleaner. Check the hose diagrams available elsewhere on this very website for some drawings. (The 74 2.0 will be close, but might not be an exact match.)

--DD