Re: 156 2.4 JTD 136bhp TURBO Question :)
sorry, i am not Gus...
the std map sensor will measure up to 1.5/1.55bar boost, if you fit a map sensor froma 16v/20v it will measure 2bar or just over.
The VNT turbos are quite weak in the presuure they can handle, so if you have a vnt small frame, don't kid yourself it will handle 2bar without exploding.
A Gt28 is good for boost, but probably won't spool 'till 2500rpm, don't know much about a 23, not the biggest of turbos?
The engine is strong, stronger than the turbos alfa fit to them, if you run 1.6bar you'll breeze it.
There may be a payoff between imp & emp which will have an ideall boost pressure, but I am sure that Alfa Tuner and AHM will be along soon to give you accurate descriptions on things rather than my old meanderings!