Does the ECM read new mods? how long does it usually take to adjust or does it depend on the mod? or is it just one of things people say when they put new stuff in..."gotta break it in a couple hundred miles for my computer to read it"

and I know a tune would help, im just talking before tune what does the ECM do when theres a change...

 

If the computer it reset, it begins to learn immediately.

 

and how long does it usually take for it to...go full on...

 

It takes only a few minutes or less to start making changes to a cell BLM. There are quite a few cells and different ones for different engine loads, so it won't change them all until it has experienced driving time in them.