Thanks Tony,

I was thinking of re-testing it using the smoke machine but I'll try the technique you mention first. I was also thinking about checking the pre-cat emissions whilst also re-doing the back pressure test to confirm whether the fault was within the engine or within the exhaust.

Also, in response to Mark, the inlet manifold vacuum is 21 inHg at idle and at 2,500 - 3,000 rpm all through cold, warm-up and warm phases (when blipping the throttle very quickly the vacuum drops to zero and then rises to 25inHg on overrun). I think this is normal?

I checked to see that neither the coolant temp sensor nor the thermostat have been changed in the last 5 years (that we have looked after the car) so they will be going on. I discounted changing them because the car seemed to be getting up to 90 deg C ok.

I'll check the breather valves whilst changing the thermostat.

I'll have a look at the kV readings when the car has cooled down again.

It'd be nice to be able to find a donor AMM so as to confirm that it isn't causing a problem but I don't have one so it would be a case of putting a new one on. !!

Barney.