The only thing that comes immediately to mind is the MAP sensor - specifically, the quality. I don't know what brand you bought, but if you don't use a good quality brand then it is very possible it is either faulty or was dead on arrival. There have been multiple instances here where people have ordered these and other sensors from the likes of Eurocraparts and wonder why they still have problems. Turns out their quality is extremely questionable and parts are often faulty on arrival.
So I would double check the brand and would consider replacing that one more time with a decent brand.
Also, on this engine, there are separate sensors for the Air Intake Pressure and the Air Intake Temperature.
(10) is the Air Intake Temperature Probe (19204G) You can get a Magneti Marelli one of these for about £12
(7) is the Air Intake Pressure Sensor (457403). You can get a Magneti Marelli one of these MAP sensors for 18.59.