Steve,
The Cobra unit is similar to many other devices (most of which are probably made by the same company), such as the Digital Fuel Optimizer, that connect in-line between your ECM and the injectors. The low, mid, and high speed adjustments basically take the ECM signal for the injectors and add to the time the injectors are to be open (pulse width). These devices do work, but they are very limited compared to a PCIII, SERT, etc. And if you compare the price of the Cobra at your referenced vendor to the price of a PCIII at Fuel Moto, you will see there is only a small difference in price - less than $40. IMHO, a PCIII even with a canned map is vastly superior to one of the fuel optimizer systems. Considering the small difference in price, this is a no-brainer.
Jerry