Had same issue when mine was stock. It is just the play from the machine turning the drive train from trying to twist it from foward to reverse. Just the nature of the beast in my machine. But since you seemed to only notice this since you did all of that work, satisfy yourself and make sure all is right. I have done all of those mods as well.
09 teryx- msd ignition - water impellar - half windsheild - uni filter - standard muzzy - sdr rear bumper - hid lights - dalton clutch- water temp guage - ss108 14 inch with terra cross - dasa kebc block off plate - brake alarm buzzer - over drive plate -ssv works sound system -removable canvas top-odyssey battery- rock sliders