I get that vibration through the accelrator when the a/c starts up.
Never at any other time.
It doesn't bother me at all to be honest with you, everytime the a/c spins i feel it, but.. It's like a foot massage.

Just thinking... If you look near the firewall under the engine bay, up towards the drivers side front windscreen. You will see two silver pipes with a small black cable running to the passenger side. I think from where the cable is connected to on the black plastic clip too the two silver pipes (pretty sure there a/c) maybe that's how the vibration runs through to the accelrator pedal. (This is a total guess!)