I have run Mach 4.5(165hp), and Mach 7's(240hp)(currently) and before those I ran the the Jammer stage 5, 150HP injector.....
The main difference is the F1 injectors run smoother, and cleaner
As far as fuel mileage between the Jammers and the F1's was 1/2 -1mpg difference. with the F1's being slightly better
On daily mid-throttle driving the Jammers had a constant haze, where the F1's were very clean in comparison, literally my mach 7's are less smoky daily driving then the Jammer 5's were
Is the difference enough the price...? If your keeping that setup long term, Yes, definitely worth the money -
If your broke and just want to finally be able to smoke the crap out of your 7.3L buddy's then buy the cheap ones
I ran the Jammers for a year and a half and liked them and for the money would recommend them to anyone...
I have had the Mach's for a year and definitely like them better...
Just a choice you have to make between the pocket book and performance
Lavon