Neil,

I'd really look into worn bushing/loose shaft in TB. Get that hunk of American iron you call a lathe :) up and running, make some bushings.

alistair

PS or buy one of tencentlife's vacuum switches

On 2012-06-21, at 5:25 PM, neil n wrote:

> 
> I really have to wonder if there's enough play in the engine mounts and/or
> transmission mount, that a cycle of movement happens in the drive train
> that pulls on the accelerator cable, causing the throttle valve switch to
> open when decelerating. I have purposely left a little slack in the cable
> to compensate but this may not be helping.
> 
> Neil.