Sultan CTX Widebody (A) [QQ1842TN]

When i first bought this vehicle it was silent and i made a post but since then like 3 days ago after the mechanic update for the city my car started making really loud gunshot like noises when you start it up. I have recently took it to the mechanic and had it repaired and looked at and also i have parked it and put it in the garage and back out multiple times with no luck. I havent been able to drive it since i bought it cause its just so loud and turning the sfx volume all the way down just makes it way to silent. Is there anything i could do to maybe correct this? If not could you please maybe take a look at the car and see if you could fix it. Appreciate you!!!!