Sounds like a vacuum leak. My guess is you either broke or didnt re-connect the vacuum line to the modulator after the tranny work. have you tried a vacuum gauge to see what it reads. I think you need to start from the begining. If the wires were arcing they are bad or the wrong wires. Make sure you have a good set to start with. I would also replace the plugs, they are fairly cheap and also can not be completly ruled out with just a visual inspection. Assuming the car ran ok before you pulled the tranny, you need to look at what could have happend during that procedure and for gods sakes stop throwing parts at it.
More info would be helpfull also, what year, what tranny etc