my Corsaro now has 2500 km on the dials but all of a sudden lately I'm experiencing a rather annoying jerky, on-off, then again holding in response in the below 4000rpm region and in the lower throttle percentage region.
The engine also seems to spit back mixture into the airbox. It huffs and puffs and seems to want to blow my house in.....

It does run powerful, nice and wild once I get above 5000 rpm's but riding in traffic or taking a roundabout like any normal mortal would, is a real intense and sometimes nerve wrecking ordeal.
1/ So the dealer replaced the champion spark plugs with NGK's but that didn't do the trick.
2/ Then the dealer said it might have taken water in the fuel tank due to a blocked drain in the fuel tank filler, however after having added two times a fuel additive that is said to bind water, it does not improve the on-off and hesitating feel when trying to smooth-handle at low throttle settings.

Ow yeah, I get 140 km out of a full tank before the reserve light pops on.
3/ The computer tells the lambda sonde is in closed loop and all other parameters "appear normal", dixit the dealer.
(I found out on the net that:
ECU Modes:
OPEN LOOP - this is the mode your ECU is in until the coolant temperature and a couple other sensors get to operating values. This is also true when you are at WOT or when throwing codes/ CEL's
CLOSED LOOP - the ecu uses information primarily from the Oxygen Sensor and adjusts fuel delivery and timing to achieve minimum emmisions, better gas mileage and power.)
4/ I'm thinking the lambda sonde might be giving erratic info to the ECU, however the dealer says once after 800km the ECU simply doesn't receive any more input data from the lambde sonde. Is this true?

http://www.ducati.at/news_morini.htm
Tech Talk: Morini-Mapping mit Lernfunktion
Interessant: um ein Optimum an Fahrverhalten und Benzinverbrauch zu erzielen, wird die Einspritzung während der ersten 400 Kilometer einer jeden Moto Morini ständig optimiert (basierend auf den Werten der Lambdasonde). Gut für die Umwelt, gut für den Fahrspaß! This text says the first 400 km the ECU is learning. That's all. It does not say the Lambda Sonde stops giving voltage info through.
Should the lambda sonde be replaced to end my sleepless nights?

Thanks for any feedback on this or solutions on similar issues.