I am surprised at the word "TUNED"..
What did the mechanic do?
Please remember all new cars with ECU/ computer do not need tuning. Only maintenance they need is changing of oil, oil filter and air filter.
You guys first get your car screwed up and then seek advice.
I would recommend that you check your air filter, please put new original filter.
Further, use air conditioner as battery temperature also effects the performance car.
Pls share what did your mechanic do..
Have you changed tyres?