Modern Vespa

Hello, ive got a 2009 400ie.
Scooter is on the center stand. When Turn on ignition 0.7 sec immo flash, after stay off, check engine light is also off, tilt lock is off. After starting 4-5 sec the engine is stops, no idle. If I try accelerate for higher rpm it is rumble or drowning and stops. The diag IAW thx for Pilaf cant find fault codes, test actuators all working. Only 1 thing what I find, the intake pressure is always 0. Can anyone tell me of the working engine this value in idle or hihger rpm for example 3000 1/min?
What is the reason, blockage or dirty throttle body?
Where meassure this the ecu?
Thank for your help.
Rob

if it's anything like my vespa 300 hpe, the sensor is in the barrel of the throttlebody

I bet the valve clearances have never been checked.

also seemingly the map value is only valid when engine stopped

https://manuals.wotmeworry.org.uk/useful%20info/magneti_marelli_miu_g3_information_14854.pdf

Thanks the fast comments, its only 20k kms, if the engine is running independ the actual rpm, a short time idle or sometimes i can get 4-5k/min with play the trottle, the value is always 0. But I think the ECU calculate the fuel from quantity of air by sensor. So i think it will be not zero, when engine running.