My S3 (1.8T AMK) has a stage 2 custom map and when first remapped it would hit approximately 24psi before tailing off to 22psi which it then held across most of the rev band.
Recently however the car struggles to make anything above 20psi and usually holds 19psi across the range.
Vag-Com shows no faults.
I removed the N75 from the TIP and plugged the tip, left everything else on the N75 connected and just left the end that was in TIP "open" as it were.
Took it for a drive and the car then made 22psi and held it across the range.
Are these the symptoms of a faulty N75 valve?
I shall be performing a boost leak test this weekend to rule that aspect out.