Modern Vespa

Yes I know I'm running mega rich as by the oil as I'm dialing in my jets but the connection between the two pieces is awfull, is there anything I can do? Maybe it will plug up on its own with soot or permatex copper rtv

Looking at pictures online both springs are installed but I'll doubt that helps as the leak is coming from the top where adding more tension on the bottom will open it up more

You could try sealing compound as you describe

Or you could if the connection pieces bottom out to each other then it may be possible to add a sealing / o ring

I'd remove the pipe, 100% degrease it, then reassemble the joint with copper RTV.

Once you get the jetting correct it will stop drooling. You can make packing with wood-stove door rope if it makes you feel better. It's a lot less messy than rtv...

If it's a double walled header pipe, anyway. Mine is, but it's so old it's a Leo Vinci. I don't think they changed anything when they changed the name to Leo Vince.