1st 2nd and third gears, no problems or concerns, if however I apply full throttle in 4th (Motorway driving overtaking type scenario) my boost guage acts very strange and the car feels wierd.

The boost guage in the first few gears behaves normally i.e tick over and off boost it will show negative, when throttle applied, it will rise, peak and fall back slightly to a steady pressure. In 4th however, if changing up from 3rd, I fully apply the throttle and the boost gauge needle flies round to about 17psi then drops back to about 13. The car really feels like it is flying during this phase. If i then let off the gas and then reapply the needle does the same thing.Could it just be momentum (not of the car) making the needle swing past it's actual reading for a split second? it seems to really fly round. Apart from that the car runs ok and nothing else is worrying me. This actually doesn't bother me, just wondered what could be causing it or is it normal?
Car feels much faster in the cold to, is this normal?

ta

 

It is overboosting. Check oil level and clean out the restrictor and solenoid with brake cleaner. Let it dry before reassembling and starting the engine. If it persists change the restrictor on the compressor outlet to 0.1mm larger to cure it.