Just a little update to say that the TTRS/RS3 pump does fit a 56/07 S3 8P!!
I've been running one now for nearly 2 weeks and it's caused me no issues at all. It has also cleared a hesitation issue I had under load. The logging now shows the right numbers too, which I'm chuffed to bits with.
Was a little bit of a fiddle to get it in. We had to swap 1 hose from the original pump over, no big deal as just cut the new one, lube it up, slip the old one over and clamp it up. 2nd thing that was different was the (i think) return (could be feed I can't remember) from the swirl pot. This issue was overcome with a simple 90 degree bend of tube which now sits in the correct hole.
Not very informative or descriptive I know, but I searched high and low for information on this before biting the bullet, so hopefully this will help someone else when making the choice for uprating their LPFP.