Knocking noise when giving it the beans!

So, i have just got my N/a back from the guys at AFR, they did a brilliant job swapping it from auto to manual, cheers again guys. I didnt notice it before (maybe because i only drove it twice on the motorway?) but when i floor it and pick up speed i get a tumbling noise coming from the nearside rear wheel area, i odviously thought of the wheel bearing, is there anything else it could be? The wheels are done up correctly and the tyres have no bulges.

Its wierd, it doesnt correlate to speed, if i gradually build upto 70mph etc, gradually revving to 5-6k i dont hear anything. If i floor it (and only when i floor it) from static or low speeds the sound begins when i pick up speed, the faster i go the more noise it makes as though it is 'tumbling' faster, as soon as i change to a higher gear the noise goes again as though the noise correlates to how much force is being put through the transmission and wheels?

Anyone else had this before, the old search button showed up bits on the wheel bearings, it may well be that, i will jack the car up tomo and see if theres any play in it.

Cheers folks

Driveshaft perhaps?

Had a good look under the car today, jacked her up and spun the wheel, nice and free, no play in the bearing from what i can see, there was however a large bit of dead fox stuck between the suspension shock and arch, nice. Im guessing it was this poor creatures remains making the noise, i can remember hitting the stupid thing but thought nothing more of it at the time, never mind!