I installed a bleed valve in my '99 GTT. I followed instructions from Lee's site (http://www.scoobmania.freeserve.co.uk/my_impreza_mods_boostinc.html) and put the bleed valve in hose C.
My results after some adjustments: Boost peaks almost immediately at 1.25 Bar (good) but then drops to the original 0.95 Bar (not planned).
Am I overlooking anything or is my car just smarter than me? Would shortening the wastegate rod help?

 

I think the later models (MY97 onward) have smarter ECUs which may think around the bleed valve -- but no experience with these later cars so someone else may have better advice ....

 

Bleed valves are an inaccurate science! I found that putting a valve in the Wastgate tube caused wild over boost and that putting one in the hose from the turbo caused steady linear boost up to about 13psi then wild overboost set in again. If you have put the valve in the hose to the solenoid then put it as close to the solenoid as you can get it. Alternatively checkout the Dawes Devices mechanical boost control valve, It seems to control the overboost better with very little overshoot.

 

Is there anyone that got a bleed valve to work properly on a later model GTT that recognises this (and has a solution?)
I would like sustained boost above the standard 1 bar level.

Current setup: In hose 'C', from the original T-piece: 5 cm of added hose, 1 T-piece, 2 cm of hose, 1 cheap fishtank valve 90%open.

 

Yes, the Dawes Devices mechanical boost control will do what you want, $35 or $50 for the deluxe kit (extra tubes). Just be sensible with the settings............