A whole lotta rumbling going on
 

Car is a MY99 Impreza Turbo, 58k miles.

1) Occasionally on startup, (not noticeable on cold startup) there is a grumbling from the right rear. As this is where the petrol tank is could it be the fuel pump on the way out?

2) Rumbling is also coming from the rear and is noticeable on trailing throttle slowing from about 2500 rpm, (it may also happen at higher revs but engine, exhaust and road noise drown anything out). Wondering about dif. bearings being the cause.

Thanks in advance

nobody?