pcm question

[bownz4]

This maybe completely wrong but I read this on a forum and wanted to know if it was right. Someone was saying that over time your truck will "adjust" itself to compensate for mods. For instance, when you put a CAI system on your truck supposedly it runs fairly lean. What I read was that over time your truck will actually adjust itself to where it will run less lean and try to correct itself.

I have had CAI on my truck for a couple months now and have been waiting on a custom tune, if this is true then my truck is running at a different mixture than a stock truck, and if so when I do get my custom tune should I reset my pcm to what it originally was.

I know that's a long question and I may just be splitting hairs, but I was just curious. - Thanks!