Q: I brought a 2006 Infiniti g35 coupe. When I start it up it sounds like a race car, when I press the gas it gets louder until I let

The previous owner might have modified the air intake (a box like component holds the intake filter) but the noise you are referring to is probably caused by a defective exhaust and/or aftermarket exhaust parts which result in excessive noise. Of great initial concern is the possibility that the noise is accompanied by an exhaust leak. Unfortunately, when systems are modified that increases the risk of faulty connections. Noise will damage your hearing but leaking carbon monoxide can kill you so do get the source of the noise identified. A mobile mechanic can inspect the vehicle, pinpoint the cause of the noise and give you repair options. If the exhaust was modified and you desire that it be returned to stock, with the accompanying quietude, the mechanic can estimate for you the least cost strategy to accomplish that. The service to request is exhaust noise diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.