Hi Stealth_RT, sorry to hear you had glitches (still got them?). It's most likely something external to the speedo, maybe the schottky diode or the power capacitor is the problem as you seem to have found already. It's always a good idea to try disconnecting them to see if you still have the glitches. As Eric has suggested, try your MX in another car and see if that works ok. If not it could be a problem with the electronics, if so it's a very uncommon problem but it can happen. The MX design is as good as you can get to not cause glitches.
Fred I've received your message, I will reply later today when I have the answers.