Easy, as Ben said, disconnect the air bag plug & free the wire retaining clips then undo the 4 torq bolts
When its out the car have a good look at the seat rail & you should find the bolts on the side of the rail, they pivet when the seat is raised & lowered - if that makes sense
take the seat out of the car, remove the seat mount plastic covers, from memory there are some fixings in either side, you should find them, tighten them, it may only be a bit but that sorted my set
it nearly drove me mad
That may be why I’ve had 3 mk 3’s
Funny you say that about the S1 chassis, on my last 2 ring trips I saw hardly any Audi’s apart from S1’s, they were plentiful