I wish tuning a standalone only involved modifying VE tables! You have to understand the thousands of man hours that go into developing a PCM like GM’s. When my son and I took Greg Banish’s Engine Management class he explained how much time and money went into to every aspect of the “tune” on a PCM. For example, just to get the “Cold Start Enrichment”, “After Start Enrichment” and the “Warmup Enrichment” in the PCM working correctly Greg and several other “tuners” and support personnel were flown to Alaska during the Winter. They spent an entire week tuning just those parameters! The PCM’s like GM’s have hundreds of other “tuning” parameters like these already worked out for you.
So to answer your question about the difference between a standalone like FAST XFi and a factory PCM… when tuning a standalone system you are primarily on your own. Yes, the VE table tuning is primarily the same but you MUST understand the modifiers affecting the VE tables and what impact it will have on the final product.
Please don’t think I am pretending to understand everything about this. I’ll be learning this stuff the rest of my life. I encourage everyone to learn what you can and ask questions when you’re uncertain.