Everybody has different opinion about what to do for the intake system on the WRX.Some short ram,some C.A.I.,and some modified/stock oem airbox.I personally use the stock airbox,Green drop-in filter,and a 4" velocity stack in the inlet hole.Reliability is no problem unless you don't have the wheel well/inside fender liner
The inlet hole is at the same hieght as the inlet scoop.It is alittle bit louder(especially with a high flow filter and TBE).Summit Racing sells a 3" I.D. velocity stack that fits right in the inlet hole.The stock elbow is about 2 3/4" I.D. Open up the hole alittle bit.