Gasoline savings in Chevrolet Astro

Hello friends, I need a little help,
Since I am about to acquire an Astro Chvrolet of 1987, this has a 4300 cc V6 engine. And they are reputed to be very gaston in fuel, but I find out that there is a chip that is installed and it modifies the entire configuration of the ECU (in English: Engine Control Unit, where I understand the computer) and that it does not cost more than 100 dollars and you do it yourself in your home in 10 minutes only changing the mint chip. But here in Guatemala as nobody knows about this, so I would appreciate a lot if they gave me information where to buy them.

Thanks in advance and God bless you !!!
Greetings