OK I have a 2000 Mustang v6 that I just completed an SC swap on. After I tuned the computer with my SCT I started noticing weird problems a couple days later. I have returned the computer to stock and still same issue. The speedometer jumps around and the car starts bucking and misfiring. I checked the codes and I got p0340 and p0721 which are codes for the cam sensor and speed sensor. Well I read that code p0340 is usually a bad alternator so I installed a new motorcraft one and still have the same problems. I am now thinking my pcm is bad because it is an intermittent problem.

Any help with diagnosing these issues would be greatly appreciated.