Which TBI system is better?

[fastacton]

So what's the difference in the force motor that would cause one to need to change to a different PCM?

I'm not an expert on it, but I believe that the force motor operates at a different frequency and has a cleaning cycle that the '7427 doesn't support. I've heard of people using the early trans with the '7427, but not sure how long they'll last like that.