Hi Pit-Man. If you don't have an EFIE for adjusting the O2 sensor signal, you're missing out on the most important sensor you must treat to get the gains from your HHO devices. There are a number of documents that cover this at http://www.fuelsaver-mpg.com/documents.html
. Read the first 2 documents for the introduction to the subject of oxygen sensor signal handling, and how it works.
After the oxygen sensor has been handled, you should get a big improvement in fuel economy. If you want to go for even further gains, see the article Tuning For Mileage, which is also on the documents page. It covers the handlings for the MAP, MAF, IAT, CTS and other sensors. For instance, I don't know if you're using the correct method for your MAP. But it's covered in that article. There are 2 main types of MAP sensor, and they each have a different handling. Make sure you have the correct type for what you're doing with it.
Go ahead and read those articles, and post again if you still have questions.