hi there my friend has an impreza 555 and his car is only boosting to 0.4 bar it is all standard can anyone help me and let me know wot the standard boost should be on this car please many thanks stephen

 

It might be stuck in "limp home" mode?? not sure on the boost level but it should be more than that. Is his engine check light on? 555 Impreza is that a my1995?
He should be able to check the fault code reader (might help diagnosis)....this explains what to do;

Scoobypedia | Trusted knowledge for everything Subaru | Knowledge / Reading ECU Fault Codes

Gareth

 

Here ya go mate, there should be a sticker on the lid, you can cross refer it to this list

Boost Targets & Fuel-Cut Limits

WRX/STi Saloon ECU's 2C, U8, W6, W9 - As above, 11.47psi held to redline. Fuel-cut 14.57psi

WRX (1995/96) ECU Z4 - 12.71psi, dropping to 11.78psi @ 6600rpm. Fuel-cut 15.65psi.

UK/Aus/Euro ECU's V7, 7D and 6D - 11.47psi, dropping to 9.47psi at 6600rpm. With Fuel-cut @ 14.87psi

UK Prodive ECU - 13.33psi (peaks to 13.64 @ 5600rpm, drops to 12.71psi @ 6600rpm). Fuel-Cut 15.65psi.

STi RA (1996) ECU 7K - 13.17psi (peaks to 13.64psi @ 5800rpm). Fuel-Cut 15.96psi.

WRX Wagon ECU V9 - 10.55psi dropping to 6.84psi (starts to drop @ 5000rpm). Fuel-Cut 13.79psi

 

when i had my 2000 turbo mapped by zen it was boosting low like that and it was a faulty dump valve . fixed by paul and turned into a rocket