the turbo timer cools down the turbo by allowing it to idle... running more oil through it and cooled water
it also helps with heat soak
a few ppl have found that when they go to the shop & stop then buy whatever they're gonna do then come back to the car it's a little harder to start
so by running the engine for a min before shutdown is just good overall... you need a fancy $200 turbo timer, just as long as it is settable for 1min to say 5mins it'll work fine
the boost controller doesn't get altered by the ddp