F.U. stands for Free Updates since you can change the calibrations on your chip as often as you'd like at no additional charge!  
FU™ CHIP - DISCONTINUED
 
We are pleased to announce that we will be replacing the current FU Chip with a new design in October 2012!
 

We will, of course, continue to support our current FU customers.  Please call us during our regular business hours or
e-mail bill@phptune.com with questions.