Hi Steve and Donald,
when I was working on hydrogen boosting diesel engines we did a lot of exhaust gas measurements.
We normally found that Nox stayed the same or slighty increased, CO2 very small reduction but CO was almost eliminated along with hydrocarbons or HC.
This was inline with our theory of the hydrogen promoting better combustion.
We also found a point which I called the top of the bell curve where we had no further improvement of producing more hydrogen (around 4 to 5% of the total fuel value) as it had reached the maximum burn and then became a very inefficient fuel replacement. (fuel gains dropped off and began to reverse)
This is well and good when burning diesel.
We also got a similar performance increase when we just injected a little water vapour mainly on power and efficency
We also tested injecting in EGR systems etc etc.
Now when it comes to recirculating HHO exhaust fumes, appart from a few HC from the crankcase oil, and a little water vapour, there is nothing benificial in recirculating it. This would explain why when burning HHO as opposed to fossil fuels you will see little improvement.
With the Anton cell the thing that interests me is the reporting of amonia fumes. This occurs if you are using urea or some other similar compound in the fuel. However in their case I have no way of explaining it as the must be forming a little NH3 somehow.
I know you know all of this Steve but I hope it might be of help to you Donald
Mark