EyeTV software version 3.6.3 and above can use two of the EyeTV Netstream 4Sat tuners by default. The other two are reserved for mobile use.
However, you can try a special command in the Terminal, which is a currently experimental (unsupported) way to use four tuners all at once on your Mac.
1) Quit EyeTV
2) Open the Terminal application, from the Applications/Utilities folder
3) Enter this command into the Terminal
defaults write com.elgato.eyetv “max SA