Process West Raw Silver Billet Tumbler Generator Valve (TGV) Delete Kit MY99-00 Short

Tumbler Generator Valves (or “TGV” as they are most commonly referred to) can be found on Impreza WRX, Forester Turbo and Legacy GT models from 2001 onward.
Their prime purpose is to reduce emissions from cold idle to meet standards governed by the EU emissions regulations (similar regulations also exist for both the US and Japan). Whilst this may be good for the environment it does little to aid the performance of your car and it’s not uncommon for the sensors and motors connected to the TGV body to fail (leading to “limp mode”, CEL lights and ultimately considerable expense in replacement parts and code clearing).
The standard TGV’s are similar to the design of your throttle body, encompassing twin “butterfly” valves in each tumbler housing to control air flow. Even when fully open these restrict the flow of air traveling into the cylinder head ports, reducing performance. This coupled with the possibility of sensor and motor failure mean there is good call for an improved alternative!
With the port profile machined to suit ported heads these are a simple upgrade to maximise airflow in all conditions. The upper flange surface is O-ringed for a perfect seal to either a stock or aftermarket plenum. Fuel injector ports are machined in such a way that either 11mm or 13mm diameter injectors will seat without needing any adaptors, just use the supplied Viton O-rings as required. Fuel rail mounting points are the same as stock, so it is possible to use this with other aftermarket fuel rails.