Modern Vespa

Sorry for another one of these, so I'll be brief. Pops when I let off the gas, throttle cuts out when it is not wide open. I cannot cruise at 40 mph without it jerking, but at WOT it seems ok. Does not have the same power as when new. Hard to start. Hesitates on initial acceleration. Top speed is down. All this within 4 days. Seems to be getting worse. Scooter is S 150.
What I have tried: I did disconnect the evap hose and rode it for a few miles, still backfires. Cleaned air filter, yes there was gas in it. Sometimes I'll stop and unscrew the gas cap, seems to get better, but does not last too long.
My car mechnic told me that it sounds like it is running too lean. Makes sense with what I have heard here. I now will bring it in to the dealer, but I would like some idea of what the problem is to cut down on his labor (my money)
I am a little disheartened with the fact that this scooter is 2 weeks old and already funky. It reminds me of American cars back in the 70's and 80's (would fall apart as you drove it off the lot). I only say this becaue of all the other issues I have read concerning other lx 150's. Has Vespa let their popularity go to their head, and overlooked QC and design? I should not have to remove parts (evap system) or put holes in my gas cap to make it work. This thing is new. Everything on it should work! Well, I will not get too heated untill I discover the problem. Maybe it is simple...

That scoot is still in warranty. There should be no charge to you for correcting any problems. Don't dink around with it yourself.

I'm not saying that this could be the answer...but I also disconnected my evap tube and disconnected the overflow hose (filler neck connection) to the evap canister (this supposedly can cause a vacuum build up in your fuel tank).

See the attached link...did this last weekend...pics included.

https://modernvespa.com/forum/topic50298?highlight=

Hope this might help your situation...