2001 Toyota Camry not accelerating smoothly

Usually when you have a random misfire it is something that affects all of the cylinders. Things like not enough fuel getting to the injectors (possibly from low fuel pressure), low compression (if the compression is low then the engine is worn inside), etc.
The P0301 code just means that that specific cylinder has a constant misfire. It sounds like you have replaced most of the ignition system. I'd start looking into the fuel injectors. Sometimes the easiest test is to swap them and see if the code follows.