This is what my local mechanic/turbo place does. He doesn't subscribe to any of this dawes/needle stuff. He's had 4-5 blokes come in with dawes valves and stuff, and hes ripped it out, tinkered with the MAF voltage, and the owners couldn't believe the difference when they picked the car up.
They also do this when they fit a chip. He didn't reveal specifics, but showed me some dyno sheets to prove it.