Engine Noise heard when accelerating from slow to fast...??

[rodberg007]

Guys,

I was driving home tonight and because it was so humid here I just happended to have the windows open in the car but while I was driving along and noticed I had a clear stretch of road ahead I decided to pick up some speed from 60kmh and when I did I heard this pinging noise from the engine - like the sound of marbles or stones going down a pipe - not sure if that's the best way to describe it but I think you get the idea, so if anybody else has a 3.0i petrol maybe they can provide some technicla information that might explain why I'm hearing this noise when accelerating. The engine didn't perform any different and it did have plenty of power in it but just wondered if it's anything to do with fuel I'm using or the way I drive which is mostly city driving I do anyway during the day. in and out of traffic and stopping and starting alot in saying that I used to hear it the odd time as well on my 01 325Ci auto when going up a hill I would put the foot down a little bit and heard a similiar noise ... so any suggestions to that affect would be most welcome!..