o2 spacers?

Hello everyone,
I am new to the forum. New to hho also. I have been doing alot of research. I have been getting the materials to make a electrolizer. I recently bought a new to me pickup A 2000 ford ranger with a 4.0. It gets 15 mpg. I cant afford to put gas in it. My questions are:
What purpose are o2 spacers?
Should i use o2 spacers and a EFIE?
Does anyone have an opinion on a quad digital enhancer from FuelSaver-MPGInc?
If anyone has a ranger or explorer with a 4.0 and has some suggestions I would appreciate it.I dont have alot of extra money to use for experimenting. When I buy an EFIE (if I need one) I want to make sure I purchase the right one.
Thankyou

O2 spacers are a waste of time and money.
The Fuelsaver IFIE is your best bet.

EFIEs definitly provide better results but i have found o2 spacers work great on small engines specially in Hondas. Civic and CRV.

The problem with o2 spacers is that it decreases mechanicly a fixed % of what the sensor reads. If you magicly compensate that % with HHO you will get mileage gains. But 90% of the time you will only get the check engine light.

Hope it helped