Disco 2 Vibration Pedal

Hi all, not long bought a discovery 2 2003 with 128k miles on it, purchased it to build a fairly simple and stock overland setup. Currently only got mud terrains on stock suspension no lift, bags have been replaced with springs on the rear and its a non factory ACE model. Have had a few outings in it and it's not had an issues on the trails however the last time I took it out when going over bumpy sections/ruts I have feedback of heavy vibration that comes and goes gradually through the acceleration pedal which seemed to be getting worse and worse as I came to the end of the trail. I've searched throughout multiple forums and Facebook and can't find any conclusion to what it may be. It's been totally fine since I've been back on tarmac apart from going over a long speed bump at decent speed while accelerating off? I've checked the props, half shafts, bushes and all seems solid and okay. So I can only assume its drive train related due to only being when on the accelerator and it's been completely fine since I came off the trails? Any ideas before I start replacing things? Plan on going to use the local pay and play as I know the owner for a test this weekend to see if I can come to a conclusion otherwise..

Thanks in advance, greatly appreciated