Here are pics of the new pedal from all sides, courtesy of ECS
and Tim has the instruction how to change it on his E31, same procedure on our car

He tells us:
A quick look at Repair Manual implied that replacing the throttle pedal (35411154936 was a five-minute job. Well, it seemed easy, and it probably is if you know the trick to it, but I struggled for around 30 minutes until I worked out how it was held in place. Right, here goes then.
The most important point is that the pedal is held in place at the lower fixing by THREE clips on the pedal, only one of which is immediately obvious. The fixing point on the car is a metal blade with three apertures.
The pedal itself has a central clip that is used to pull the unit down onto the blade, as this is pushed upwards it enters the central aperture and lowers the pedal into position and helps lock it in place.
The main catch can be shown above, it is shown in the un-locked position, below the mangled remains show the catch close to the fully locked position where it grabs the metal blade.
I though that was the entire locking system and then struggled to lift the pedal from the blade until it became clear that there was two other clips - and they have to be pretty mangled for removal.
Above you can see there are (apart from the central catch) four slots, and between each pair of slots is a plastic tang. Behind both tangs is a shaped catch holds the pedal to the blade - you can pull as much as you like. those two catches hold onto the blade as if they were made of steel - and only a complete mangling of the plastic between each pair of slots will remove the pedal - here's how it's done.

First, get a feel of where the central clasp is.
And then use a thin screwdriver to lever it downwards until it is flat on the carpet, that's the central one released. Now use a fat screwdriver to push the carpet downwards to get access to the two other clips between the pairs of slots.
It is just a case of using a small screwdriver to remove the plastic between the slots (by removal I really mean butchering) - once those are mangled use the same screwdriver to poke the central catch through the central aperture in the blade to fully release it - and then lift the pedal away from the blade.
It would be reasonably easy to do this as long as you are aware it needs to be done, if you don't (like me) it takes a little while longer. Where the pedal connects to the linkage above, it is held in place with a protrusion on the shaft - and that needs to be aligned with the slot in the pedal.
So, with a bit of fiddling, rotate the pedal around the linkage until it slides off.
Slide the new pedal onto the linkage.
And push the bottom of the pedal firmly over the blade.
Finally, lift the central catch upwards until it clicks against the back of the pedal.
Time for a cup of tea!