CabrioArtie

Installing Koni Acitves with M033 springs in the rear and the original Monroes had this part on the lower end of the shock called "Supporting mount" (993 333 110 01), see pictures of the part on the original shock and off. Doesn't seem like it fits with the M033 springs I'm installing,

Can someone confirm whether I need to install this part or not. Thanks.

Todynot

I did not. All seems fine.

pp000830

Looks like a foot/bushing to take up the clearance between whatever previous spring/strut combination was on the car to avoid the spring slopping around on its perch. Probably came with the old springs if they were not OE or the previous struts. In either case most likely not needed as if your new struts required such a thing they would have come with them as part of the application kit.
Andy