While I have used my 1996 OBS to write this mods page, this modification will work on any 1993-2006 Impreza, and quite likely any other Subaru model. Simply put, coolant runs through the throttle body to keep the butterfly from freezing up in cold weather. Many locales never see cold weather, and really do not need this feature. For colder climes, the mod is easily reversible. By taking the hot coolant out of the throttle body, you will decrease your intake charge temperature and gain a few horsepower. Questions or comments may be directed to me here.
You will need a few bits to get this done- two caps and one hose barb. I strongly recommend getting a brass barb, as the plastic ones may not be up to the heat of the coolant (over 200 degrees F at times).
Here is where we will be working- this may be easily accesible (as on my car) or you may have to remove the torque box or intercooler, depending on what model you own. You need free acess to the underside of the throttle body.
Here, you can see the clip for the coolant output on the driver side. Sqeeze the clip, move it down the hose out of the way, and pull the hose off the barb on the throttle body.
This is the location on the passenger side of the throttle body. It is rather hard to see and photograph, but the process is the same as for the driver side. Squeeze the clip, move it down the hose, and pull the hose off.
Now, all you need to is insert the barb into both ends of the free hose, and replace the clamps, as seen here. Push the caps over the barbs on the throttle body, and you are done.
Standard Disclaimer: Modification of your car involves risks and may void your warranty. I can not be held responsible for the modifications you consciously decide to undertake nor for the results of doing so.