The issue is two-fold...
The engine starts fine and idles smoothly. But upon acceleration, a) the car will stumble/lurch and lose power, and b) the speedometer needle will bounce and/or bury itself. A drop into neutral and the speedometer reads actual speed normally. The two problems began to happen simultaneously; one did not start up before the other.
Any ideas on what could be causing this problem? (Something electrical?)
Thanks, Brian