Paul, thanks for joining the fray.
With regards to vacuum leaks, I have tried the carb. cleaner spray around technique. If I loosen the brake boosters vacuum supply at the manifold I get a significant increase in revs., and as mentioned in a previous post above the duty cycle etc. go completely haywire.
New track I might try that was suggested to me today. I don't know the previous owner or the service history (if any) this vehicle has been subject to, with that in mind if the mixture has been off for some time and misfires etc allowed to continue its possible that the catalytic converter may be stopped up. It will idle fine, but as soon as I try to put more air through the system that's when it starts to choke up. So I'll disconnect the pipes and see if it helps. I live deep in the country so noise is not a problem.
Your thoughts.
Michael