Im curious to know how well ECU can adapt new values after changing better flowing exhaust system.

(read: TBO-Back with hi flow/ metal cat)

Revo and APR can be modded afterwards but how much gain can be achieved more than the gain

that is got when ECU adapts to new lambda values and ignition points?

For example Is Jabbas maps different for orginal exhaust and performance exhaust, what are the differences?

Can some jabbas, Revos, etc's pro enlighten this matter?

Can't speak for the other companies, but Jabba can "tweak" a re-map any time you like to suit any post re-map mods....for a small charge of course

I assume the others are the same.

How much are these "small" charges btw?

Well thus far I have seen no difference in a car (mine) with APR 98 pgm and all the above mods against a jabba k04 + mods. Very similar figures. Road he may well kill me owing to the k04, but thats a different story.

So really as you have answered your question to my knowledge, the differences are minor and the ECU learns to a degree or 6.75