I have just bought a 2005 Astra 1.6 xsi but I am finding that it is making a deep (almost as though there is a hole in the exhaust) noise when you accelerate plus the car has very high fuel consumption. Driving around town I am getting around 300 miles to a tank of petrol

Can anyone tell me if the noise is a natural xsi sound (the garage that I bought it tells me it’s a “twinport” engine sound.