Modern Vespa

Hi,
I own a 2011 mp3 400 and my scooter often dies at a stop while a popping sound of a backfire from the exhaust occurs.
Iv'e noticed a black spot on the connection between the exhaust and the pipe as in the picture.
I'm wondering if an exhaust replacement is needed although it sounds fine (a little bit of some high pitch clicks coming from the exhaust but nothing to alarming).
Also my fuel economy is very bad.
Any ideas?

Probably the graphite ring inside the muffler pipe needs replacement

Does the graphite ring can dies the engine and make high fuel consumption.
I have problem with that ring on my older bike beverly 200cc with carburetor and there no problem except bad noise, but I don't know with injection engine is there difference.

Don't do anything with the bike.
Buy a can of injector cleaner, poor it in the tank the next 4 or 5 fill ups evenly.
If that doesn't help do what you want with the bike.

It's running to rich and it looks like the connection is not all the way seated together along with the clamp being a little off target by not covering the bottom of the slots where all that soot is coming from.

Graphite ring is caput.
Get it replaced they are very cheap to buy.