If the Instrument Voltage Regulator (IVR) was the problem, the fuel and temp gauges would climb too. Not unheard of for a replacement sender to go bad.
This is what I was thinking, the other gauges would be reading high was well. Yeah, I don't want to hook it back up until I figure it out, I've had to rebuild a couple of cook gauges for losing a ground and its just becomes time consuming.