I am in the process of completing the Lex AFM/550 modification and decided to monitor the Vf signal before and after the modification. I'm not sure if this will be helpful in making adjustments but at least I'll have the data. Has anyone made these measurements on their car? For the limited driving I have done while monitoring Vf the signal starts at 0 at start up and after a few minutes it reads between 1.0 volts and 3.5 volts but seems to be at 2.2 volts most of the time. My understanding is you don't want a 5 volt signal because that would indicate the computer wants maximum fuel. I would like to hear from anyone that has knowledge on this subject or the adjustment process for the Lex AFM/550 modification.