The noise on my car was a definite "thump" as oppossed to a pop or bang, and was wheel rotation related (certainly sounded it).

HDDP: I checked what you suggested the first time you posted - sorry, forgot to update on that. Fuel tank capacity is normal though. Thanks for your advice though.

Car is still running fine under all driving styles and even on super smooth roads, the noise is no longer there. Weird!

B/r
Steven