Monitoring AFR is only effective if you run high ratio of methanol and water does not affect AFR. Unfortunately, water has twice amount of latent heat properties than meth. If you run 50:50, you may need an EGT probe as well.
Only the aquamist 2d system provide a pump flow signal relative to valve opening duration. On other systems, you need a flow sensor (progressive) or flow switch (over or under flow)
Here is a picture of a typical flow switch: