PutiPlot

I also managed to convert my throttle to USB. I struggled a little bit with MMJoy2, but the pictures in this post helped me a lot:

Coming late to the party, but thank you for this good guide. I was able to convert my Cougar Throttle to USB with ease. I was not able to use the attached mmjoy file, so had to set up everything manually, but that wasn't too difficult when using the pictures. The picture from mrWell above also helped to map the buttons correctly. (And helped me identify that I had mixed up some of the cables) The only issue I had was with MMJoy itself. I didn't select the correct "Auto calibration". You need to use the "Auto w/centering" or else you will only have half the effect on the axis. And you actually don't need to do any soldering at all. You can buy a pre-soldered Atmega32u4 Micro, and then use dupont-cables for connecting the Arduino (-clone) to the Throttle PCB.