1. Drive off boost for the last 2-3 minutes on your journey home. Voila. No need for turbo timer at 2am in the morning.
2. Take off slowly and short-shift into 2nd gear and then 3rd gear ASAP to minimise noise. Maintain a STEADY speed up until the end of your street. Do NOT floor it to 40km/h and then wave the "but I wasn't speeding flag".
3. Write a letter saying that you don't feel like you have done anything wrong, certainly not speeding, and explain that your exhaust makes it seem like you're going a LOT faster than you actually are. Explain that you have a standard engine, standard blow-off valve, standard wastegate, standard turbo and that any noises from the engine are completely standard. Apologise for any inconvenience caused espcially late at night, but you would have appreciated if the neighbourhood magistrate would have actually signed his/her letter. Make them feel ashamed for not having the balls to sign it.
Attach this letter to a copy of the original letter and deposit amongst your neighbours.
Simple. Respect your neighbours. Don't sh1t in your own backyard.