Hey beautiful build, very well thought out and well documnted
So at 14psi boost your only seeing 2.63psi exh back pressure, thats very good.
You also have a turbo inlet pressure reading as well (12psi) that'll be interesting to compare as I'm going to be running one to with a sealed ram air inlet to the turbo. This is on a landspeed bike so I'm hoping I may start to see positive atmoshere figures at top speed.
Good luck with the car, it looks great.
Ian