Fiat Doblo 1.6 v16 petrol

Hello! Here's the problem: the engine shakes at idle,
I cleaned the injectors, new spark plugs, the coils seem to be working, the throttle body is also cleaned,
I changed the oil and filters, I had the timing belt and rollers replaced at a FIAT service center, but they changed the belt on an engine like mine for the first time, maybe they messed it up.
I've been to a bunch of service centers in Mykolaiv, no one can solve my problem!
I've concluded that in our glorious city of Mykolaiv there is no competent service center, even our official FIAT dealer is clueless, they say they don't know how to repair Fiats with the 1.6 16-valve engine.
PLEASE HELP IF YOU CAN!!!
advise where to go.
Thanks in advance.