When I measure the pressure sensor input to the ecu, I get a constant 5v reading no matter what, this matches with one of the outputs on the pressure sensor. A different output on the pressure sensor outputs the correct voltage, which fluctuates with boost.

a) how come I don't have permanent fuel cut?
b) is there any possible reason it would have been wired like this?
c) should I switch it over and see what happens?
d) reckon I can break anything if I do?

btw, the ecu doesn't give me any error codes, and the car runs fine...

 

What does your boost gauge do?

a) Maybe because it is wired backwards
b) To accomplish letter a)
c) If your boost gauge doesn't work, then yes. Lightly drive and see what happens. Also if your boost gauge doesn't work make sure to see if it DOES work after you switch them. If your boost gauge DOES work, then it is up to you.
d) Possibly if you hammer on the car and it doesn't get enough fuel. Do things slowly to see what happens. Most importantly check the boost gauge.

 

Ok. The boost gauge is normally fine, and when the wires are switched it stops working, and the voltage at the ecu doesn't change.
So basically it looks like the ecu is not connected to the pressure sensor, and is connected to some reference 5v somewhere...