The most highly recommended and best dv for the 1.8T engine is the Forge 007p. Its a must have on a remapped engine.
http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=0006&product=FMCL007PThe reason this is the best valve by far is because the Vag 1.8T engines dont like atmospheric valves - the loud ones that you get with subarus etc.
These type of valves will cause a loss of power throw up lights on the dash and fault codes in the ECU. The ecu needs the air to be put back into the system for it to run correctly.
That said the early AGU engine has been known to use noisey valves such as baileys etc and give no running probs etc
Though im sure the engine is still not performing as well as it could by using such valves.
The 007p will give you 100% reliability and hold the boost far better than the standard bosch plactic one. (which are to prone to crack)
The 007P is tried, tested and proved to be 100% reliable.
If you really want a loud psssttt noise you can get the forge spliter valve:
http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=0006&product=FMDVSPLTRThe Splitter valve gives a combination of blow off and recirculation valve operation all at the same time.
It has been specifically designed for the many turbo engined applications that operate metered airflow management sysyems (Inc 1.8T VAG).
This means you get all the noise of the blow off valve whilst retaining the compatibility with the recirculation requirements of the engine management system.
Some people have still had problems using this valve (Car going into limp mode) see this thread:
http://www.golfgtiforum.co.uk/index.php?topic=87882.0When you order a new valve be sure to get some 4mm silicone hose for the top vacuum pipe - You will find yours has gone hard and brittle with years of being heated and cooled and it will snap!
Spring fitment:
Now you can fine tune your Blow Off/Diverter Valve to the exact needs of your engine with this complete tuning kit.
Your valve tuning kit you will find four springs and three spacers.
The strongest spring is the red, followed by the blue, yellow and finally the green which is the weakest. The spacers enable you to fine tune the settings between two spring tensions if required.
Forge normally supply the valves, unless requested differently, with a spring that will match the tension of the manufacturer’s original fitment valve. However, as many owners undertake tuning modifications some may wish to re-tune the valve characteristics to suit a given application.
If you are finding that the valve is dumping more than required or you are loosing boost pressure it is normally an indication that a stronger spring is required. Conversely if the valve is failing to dump it may be necessary to install a weaker spring. If during this tuning of your valve you are faced for example with the red spring being to strong and the blue spring to weak, you can add the spacers to the blue spring to increase the tension by small increments, thus achieving a setting between the red and blue springs.
Valve Spring color coding
Green - 5-15 PSI
Yellow - 15-23 PSI
Blue - 23-30 PSI
Red - 30 + PSI
The above figures are estimates only and should only be considered as a guideline
Please note - fitting a stronger spring into a valve will not increase boost pressure unless existing pressure is being lost. Failure to allow the valve to operate by installing a spring which is to strong may cause damage to the turbocharger.
Please note - the red coded springs should not be installed in the DVR or DV007 diaphragm valves.
Heres a fit guide:
