Scooterotica

Sorry for not being the best at explaining myself but here is my problem.
I have a 200 engine with a 25mm dellorto and a AF clubman.
My problem is that the revs don't drop cleanly it revs on for a bit then settles down.
Whilst messing around with it I discovered it works perfectly with the choke on.
I have tried different pilot jets but still the same. Apart from that his it runs great.
Any ideas anyone.

Air leak? Incorrect setting of mixture screw? Pilot too lean? Combination of these?

I have tried mixture screw and richer pilot so I am leaning towards air leak now

Trapped throttle cable. Well that's my guess.

I have checked this. Also if I put choke on it works as it should

Problem solved - loose exhaust nuts