can anyone help with low boost

[mike_j_b]

hi there can anyone help or give advice
i have an a3 1.8t ( boo hiss i know) with an aum engine . i recently had it remapped by r-tech . after the map had a small issue with boost dropping off fast . it spikes around 17psi and instantly drops off to 14 then holds at 11/12 .  i have fitted a new 007p with yellow spring , replaced the n75 and tested for leaks ( found a few small ones in the vacume pipes which i replaced ). my next job is to start replacing the check valves which is the only other place i could be losing pressre. has anyone else had problems with boost loss due to these valves as there is quite a few under there .
i have also scanned for codes but its all clear . any help or advice would be muchly appreciated

[2001gti4]

Search button, there's been too many posts on this subject to quote them all....

[jamie16v]

very simular problems to what i have, ive still not got to the bottom of it, but then i havent looked at the check valves either