I've seen this same recommendation several times before and have never done it. It seems kinda dumb to me. If I make a change that affects the ECU trim levels and don't reset the ECU, it's gonna have to learn the new trim levels and update on the next cycle. If I do the same mod but DO reset the ECU, it still has to run a cycle to update the trims. In the meantime, it'll be using defaults or nulls anyway.
If you're doing mods progressively, I'd think it'd be better NOT to reset the ECU, since the trim levels should keep moving in the same direction (ala more fuel) with each mod.
Of course, if you do something drastic (like a new turbo) you'll have to reset the ECU, because the mod should come with a new firmware anyway.
Naturally, this will be up for debate (read: bring it on) but I say don't bother: it'll just force you to have to reprogram your favorite radio stations.
