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Hey, what does the valve that is mounted to the MPS(pressure sensor) bracket that looks like a fuel regulator and has three vacuum lines attached Do? It has two big lines from the air intake distributor(Black Manifold) and a small line from the aux air regulator manifold rubber tee? It only shows in the manual under the air injection system.
It looks like it must be based on the aux air regulator? Thx Bill

That is the deceleration valve. It should have a 10mm line that splits from the air filter side (NON-SUCTION)...and a 10mm line that goes into the intake plenum right next to the line for the MPS. It then has a small vacume line lat goes to the boot that comes from the auxiliary air reguator. Its purpose is to add a very slight amount of air into the manifold...right at the MPS junction, when these parameters are met (a) the throttle is closed (b) rpm is high...like 3000 rpm plus. At that condition like from high speed deceleration or when coasting at high speed with NO throttle, the high vacume...will give you high advance AND lean fuel...because the MPS will be under full vacuum. The decel valve senses this...and bleeds a small amount of vacuum...and enriches the fuel. Its essentially a vacuum breaker. The problem is , most people either leave it poorly adjusted, or don't understand what it does. With D-jet...it is necessary. Properly adjusted, it will not interfere with performanceat all...and it can save you from detonation on a hot day.
Not many books speak about proper adjustment of this item. It is the same item that type 3 uses. Same adjustment. Disconnect the supply side of the valve (from the air cleaner so as not to cause a vacuum leak). Put your thumb over the end. At idle, there should be NO suction on it.
Rev. it up slowly...keep an eye on the tachometer. Now...drop the throttle closed. If you feel suction at any point UNDER 3000 rpm, the valve needs to be adjusted. If you feel suction at idle, it either needs to be heavily adjusted...or is defective.

At 1000 rpm...drop the throttle closed. No suction? good! Do this again at 2000....the 3000 rpm. The valve is supposed to pop open at the vacuum generated at 3000 rpm when you drop the throttle closed. Loosen the lock nut and turn the neck with a 7mm wrench until this is so.

Now....if you run higher than stock compression, or have a very tight engine, or possibly a few injection system mods, your vacuum may be higher than normal at 3000 rpm. That could cause part of the bucking problems that only happen at very slight throttle...at high rpm highway speeds...like 65-75 mph. After insuring the throttle valve is properly adjusted, I have found that setting the decel valve to open at about 3300+ rpm can alleviate this. High vacuum engines can open the valve too early at part throttle. You would think it would be great having extra enrichment, but it causes unwanted, untimed ventilation of the MPS...just like the PCV valve can do. Ray