Both will be good, with the ball bearing VF36 being slightly better spooling up than the thrust bearing VF37. (200ish RPM)

The advantage of the VF37 is that you can do a Deadbolt compressor wheel upgrade mod cheaply to it to turn it into an expensive PE1825F.

The VF37 thrust bearings can also be re-built.

http://www.wrxfanatics.com/index.php...pic=29413&st=0

IMPREZA GDB STi Stock replacement bolt-on F1 turbo "PE1825F" is the quickest response turbo in the world.
As opposed to the single-exhaust entry turbine housing on the previous GDB model, the newer GDB STi has the twin-entry, designed for smoother exhaust gas entry to the turbine housing without having exhaust interference from the left & right banks.
Torque and response at low to mid range are drastically improved by utilizing the twin entry and as allways the PWR turbo's feature the ball bearings. The compressor wheel of big 70mm easily supports monstrous quick spooling 400++ps of power all the way to the high RPM range.
The bolt on installation needs no additional work. PE1825F for Impreza GDB STi $3200 and an additional $100 for the separative actuator version.
Boost range 1.3-1.4kg/cm2 A/R: 25 (400+ps application)?Compressor wheel diameter: 70mm Turbine housing : twin-entry, Center section : ball bearings

http://www.powerenterpriseusa.net/pr...a/inprreza.htm

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