[BR3W CITY]

The 1:1 is the only one you'll want to touch. With the 1:1 ratio, you're supplying the increased pressure and allowing the injectors and your tune to handle the "specifics" of the fuel requirements (I'm assuming you have large enough injectors to supply this).

The 1:1.7's are usually something you see used on less "tune-able" cars. Its kinda like those "boost fooler" and "fuel cut defender" things you see, in the sense that its designed as a shortcut for cars that don't (or can't ) be setup with "proper" fueling.

IF for example; you were working on an FC Rx7, which due to its 80's technology and simplified fueling and computer systems, would require a full stand alone ecm and fueling system to "really" start making HIGH hp. The 1:1.7 would allow you to ramp the feed rate to stock injectors, increasing their output by a % and delivering a "calculated" increase in fuel. The idea being that you can attempt to deliver a "safe" amount of fuel...even tho you might not have the proper control of the fuel map/curve, or air metering devices to actually run it.