Evening Glen,

I wonder if the emission figures you have given are accurate. On my gas analyser, I need to get the probe fully inserted into exhaust to provide accurate figures. On the odd occasion, when running at fast idle to measure the emissions, the probe sometimes comes out and gives similar figures you have provided. You have drilled a hole into the exhaust and I wonder if the probe is fully inserted. I am not sure why you used this method which is normally used to test the integrity of the catalytic converter (before and after figures). I would prefer to see the figures at the tail-pipe in your case.

Finally, if you can't hear or trace an air leak using the normal methods, maybe you might have an "internal" air leak such as a brake servo?

Regards

Pete M