Hi Alan and welcome to Ninjette!
Could be many things causing you out-of-petrol symptoms. Could be pinched or leaking vacuum line going to petcock. Could be clogged fuel-line between petcock and carbs. We'd have to measure vacuum-level in that line to know for sure since diagnosing things across internet is difficult without numbers. Same with petcock flow-rate when sufficient vacuum is applied.
Did you find factory internal filter in fuel-line or inlet of carbs? Usually good idea to remove it and replace with external in-line filter so you can monitor it.
It may very well come back to getting carbs "cleaned". With these bikes, that's like saying I got engine "rebuilt". It's not binary thing. Depending upon who you take it to and what procedure they used and how well they did it, you may get back perfect carbs & engine, or it's worse than when you brought it in.
Do search here for "clean carbs ducatiman" to see what's really required to fully restore carbs to factory-fresh condition. Personally I think it's much easier to completely rebuild engines than to truly restore carbs.