PECV alternative
Get a three port vac. switch. I got mine from some unidentified japanese car at the wreckers.
Connect one side of the coil to a switched 12 volt source.
Find the boost light switch that operates the yellow boost light. [ Zero P.S.I. on my car. ] Connect the other side of the coil to the boost light switch that does NOT go to ground.
Pipe the common port of the vac. switch to the carb. "power valve" port.
Pipe the normally open port to a "vac./boost" manifold port.
Pipe the normally closed port to the carb "vent" port.
Remove the original PECV and plug the hole left in the manifold. Do not throw the original PECV away , there must be someone on the planet that re-builds these things?
What does all this do?
When the manifold pressure is below zero P.S.I. the power valve is connected to the manifold, and will operate according to the vac. signal.
When the manifold pressure goes over zero P.S.I. [boost] the yellow light comes on , and the three port vac switch will connect the power valve to the carb vent. This will prevent boost going to the power valve and give a full rich condition at all boost levels.
I am not sure if this what Buick intended, but it is better than a blowen PECV diaphram and will prevent damage to the carb.
If the ports on the three port vac. switch are not identified , check as follows.
Blow through the ports. The two ports that you can blow through are the common and the normally open. Energise the coil and blow again ,you are now blowing through the common and normally closed ports. The common port is the one that you can blow through under both conditions.