1994 Pontiac Grand Prix 94 Grand Prix, Electronic Spark Con

I have a 3.1 in my 94 Grand Prix. Recently, when I 1st start the car, the idle jumps way up (@2000) and fluctuates. When I put the car in drive it comes back down to normal but then the car acts erratic. The transmission shifts incorrectly or at odd times, regardless of on freeway or surface streets. If I pull up to a stop sign the car jerks and downshifts suddenly as I decelerate. I am sure the transmission is fine, just reacting to conflicting info from the engine or computer.

After 3 days, it finally put out code 43-Electronic Spark Control Failure. Checked several forums and seems like it could be a variety of things that would produce this code, however, which of those component failures would produce my symptoms?

I have a relatively (6 months) new O2 sensor and Catalytic Conv.