You dont need to use an equal amount of ammonia. I believe uh, phonon had a discussion about this some time ago. He said that using 1/16 of ammonia would be enough.

It depends on how acidic your syrup is because some have a lot of citric acid in them. The best thing to do would be to add it until the Ph reaches 11.

This article is perfect

According to the DXM zine, issue 16, article "How to get the most for your money" only a ph of 9 is required to basify DXM.
http://dextroverse.org/zine/zine16/

I have also heard of "washing" the naphtha with water to remove polar impurities before doing the extraction. Anyone got anything to say about this practice? I did it and it worked but I cant speak for the yield.