Anyone using one of these ? I have a custom, one off ,GNX style dash with VDO guages in my 87 GN. I'm running the speedo with one of Caspers hall effect senders. I've had issues off and on with the converter locking and unlocking at cruising speeds. I not only feel it but the tach jumps about 200 rpm and the scan master reading for mph jumps 8-10 mph under actual speed. Contacted Caspers and their sender is no longer available and his thought was its a bad sensor. VDO tech help said GN's electrical system and VDO gauges don't always play nicely together. VDO recommended their GPS speed sensor. Thoughts on this ?