GFB T9003 User Manual

Installation Instructions for GFB Respons T9003

Applicable vehicles:

• WRX MY01-07

• STi MY02-on

• Forester XT MY05-08

NOTE: the flange on the Respons may appear to be loose, but this is normal and does not
affect its ability to seal properly – once installed the valve will be clamped firmly.

On Impreza models without an electronic throttle, it is necessary to move the intercooler to gain
access to the hose clamp under the factory valve. It does not need to be removed completely; it just
needs to slide back far enough to reach under. These instructions take you through it step-by-step.

For Impreza models with an electronic throttle and also Forester XT models, it is usually possible to
access the clamp without shifting the intercooler. In this case, simply ignore the steps 1, 3, 4 & 5.

1) Pull off the hoses from aluminium

tubes that run across the front of the
intercooler (2 on the left and 1 on the
right hand side. See figure 1, step 1).

2) Using a 12mm socket or wrench, undo

the bolts that hold the factory blow-off
valve and remove, leaving it supported
by the hose. Take care not to drop the
bolts or gasket from behind the valve
(figure 1, step 2).

3) On the hose between the intercooler

and throttle body, loosen the hose
clamp closest to the intercooler, and the
clamp holding the hose onto the outlet
of the turbo (figure 1, step 3) Figure 1

4) Undo and remove the two mounting bolts (again

with the 12mm socket or wrench) that hold the
intercooler in place (figure 1, step 4).

5) Carefully slide the intercooler back just enough

to access the hose clamp on the BOV (figure 2).
Take care when handling the intercooler since
the cooling fins are very fragile, and also take
care not to bend the hose from the turbo too
much.

6) Take note of the position of factory valve and

then use pliers to open the recirculation hose
clamp (figure 2). Remove the valve from the
recirculation and vacuum hoses.
Figure 2

7) On the factory valve, remove the recirc elbow by

unscrewing the two Phillips-head screws holding it
on. Fit the recirc elbow to the outlet of the Respons
(figure 3) using the factory screws and o-ring.

8) At this point you must unscrew the trumpet from the

Respons to allow the mounting bolt to be inserted
into the flange hole (figure 3).

9) If the factory gasket is stuck to the intercooler at this

point, it should be removed. Scraping may be
required to remove all gasket material if it does not
come off cleanly. Take care not to drop any gasket
material into the intercooler.

10) Push the elbow into the recirc hose in the

same way as the factory valve, and replace
the hose clamp (figure 4).

11) Bolt the valve onto the intercooler using

the supplied stainless steel bolts and
replace the intercooler.

12) Push the vacuum hose onto the nipple on

the top of the valve. Screw the trumpet
back in place and do a final check to make
sure all bolts and clamps are tight.

Adjusting the Noise

The unique patented venting bias adjustment
feature on the GFB Respons lets you vary the
amount of air vented to atmosphere or recirc,
thereby changing the volume of the sound.

Turning the venting bias adjuster (figure 5)
clockwise will open up the trumpet outlet more,
making the valve louder, whilst anti-clockwise
will open up more of the recirc outlet for quiet
operation.

Turning the adjustment fully anti-clockwise will
close off the trumpet completely, and the valve will operate like a factory bypass. Conversely,
turning it fully clockwise will make it vent 100% to atmosphere, which is the loudest setting.

Typically, most Subaru engines will allow 100% atmosphere venting with no problems provided the
spring pre-load is set correctly (see below). However, some combinations of engine modifications
may result in backfiring when the valve vents to atmosphere, in which case the solution is simply to
dial back the amount of air vented to atmosphere until the problem is resolved – this is one of the
key benefits of the venting bias adjustment feature.

Do not be afraid to experiment with the spring and noise settings, no harm will come to the engine
if wrong setting is used.