Firstly, being new to the mail-list, I apologize if the answer to this is
easily available - I've looked in the various FAQs but no success.

 Can anyone help? I've got a pretty normal 2-litre, aircooled 1980 European
Transporter. (engine CU series - twin carbs, electronic ignition, no smog
control & no catalyst) I've repaired and tuned it fairly ok I hope (idle at
600 rpm with 0.5% CO, 12 ppm HC, getting about 23 mpg), but, have no technical
data . 

What is the most economical RPM range for this engine? I'm fitting a tacho &
want to get the best fuel consumption. 

Any advice or pointers would be much appreciated.
thanks,
Ben.