Turbo Restrictors

[boyracer]

Not an F1 question, but still the people reading this may still come from formulae where turbo restrictors are a necessary evil.
Restrictor design can be a quite controversial and secretive thing, but hopeful someone will be willing to share their knowledge, worth a try anyway.
The restrictor I am using at the moment has it's restricted diameter 10mm away from the blades of the turbo (part of the rules) and then expands on a gradual curve to the diameter of the inlet pipe (3"). Best way of describing, turbo is sucking thru a big 3" trumpet/ramtube.
Some other designs, while still having the trumpet shape would come out to say 2.5" (not sure of actual size) with the 3" intake hose attaching quite some way behind the mouth of the trumpet. The leading edge of the trumpet is then shaped in a full ball, with the curve on the outside of the trumpet following the inside. This apparently gives a more laminar flow into the turbo.
Suggestions :confused:
The other part that I would be interested in, my restrictor after reaching the min. diameter epands somewhat gradually back to the turbo blades (As gradually as you can get within the space allowed).
Other designs use a sharp edge, the supposed advantage here being that with the sudden increase in area there is also a sudden drop in intake temperature.
Any ideas will be much appreciated.
In case you are wondering the restrictor is for a Subaru WRX Grp A rally car, that is campaigned in the West Australian State series.
I'm not a business and certainly am not going into making turbo restrictors, just would like to know what is best to use.

[boyracer]

Is the info too secretive that noone wants to share or does no one know? Would appreciate honest answer, will accept it either way. Thanks

[Jukebox]

ever consider using the anti-lag system?

[boyracer]

Not currently using anti-lag but it is on the "to-do" list for next season. The problem still exists with the restrictor design though. We believe that the current restrictor is not efficient enough and may even be causing the turbo failure we are experiencing.
Have hopes of getting a copy of a Prodrive restrictor (to suit a 2002 Grp N) but was interested in everyone's view's although at this stage it would appear as though no one has any, or are at least unwilling to share them.