Bit of a odd one this. Got Astra G 1.6 8v. Over the weekend it had a service. New petrol filter, plugs, air filter, oil change and filter.
Now the noise is a odd one. when you drive, it will make a odd sound, not constant and no rpm etc is the same, it just happens once maybe during a gear change. It sounds like a stone is being flung off a tyre (obviously there is no stones in the tyres into the wheel arch or engine, hard to tell where. I thought it was clutch but then noticed it when taking my foot off the petrol without putting the clutch in. If i speed up in second then take my foot off around 3.5k rpm is will do it without putting the clutch in. It also only happens around 1st and second gear, the rest there is no noise.
Any ideas? its doing my head in!