These instructions are based around a stock Evo 8 MR, but should translate well to Evo 8, 9 GSR/RS models.
Preperation: Assemble the Synchronic BOV with the 1.25" hose end adapter before installing on the vehicle.
Step 1 - Remove the factory air scoop by undoing the 2 panel fasteners that hold it in place on the radiator support. Remove the cover of the factory airbox and the air filter. Loosen the 2 bolts that hold the airbox in place.
Step 2 - Remove the factory By-Pass Valve by loosening the two 10 mm clamps that hold it in place. You will also disconnect the vacuum line to the factory DV.
Step 3 - Loosen up the turbo inlet hose connection to the factory airbox and disconnect from the factory airbox. Whenever possible, you may want to re-orient the factory clamps to make it easier for yourself to access them in the future, or when putting everything back together.
Step 4 - Loosen the clamp that holds the turbo inlet hose to the compressor. You will then rotate the turbo inlet hose towards the radiator. In some installations the clamp's bolt is inaccessible. You can simply grab the turbo inlet hose and rotate it by hand without loosening the clamp.
Step 5 - Remove the upper intercooler pipe. Loosen the clamp to the DV inlet hose and rotate hose orientation towards the radiator. You will want to reposition clamps so that they are easier to access when tightening everything back together.
Step 6 - Once you have re-clocked the piping to orient the BPV's location closer to the radiator, reassemble the turbo inlet pipe with the airbox. Also re-install the upper intercooler pipe. Make sure to allow the piping to retain their newly clocked orientation.
Step 7 - Use the factory clamps and install the Synchronic DV in the same orientation as the OE BPV.
Step 8 - Re-install the factory airbox. Re-install the factory air-filter and the factory airbox cover.
Step 9 - Follow the vacuum routing instructions from your Synchronic BOV installation manual. Use the vacuum line that used to connect to the factory BPV to tee into Port A&B on the back of the Synchronic BOV.
Step 10 (For those who have the port C BOV) - Connect the boost-only source to Port C of the Synchronic BOV. Boost-only can be sourced, by tee'ng the signal line from the turbo's compressor to the wastegate actuator.
Step 11 - Re-install the factory airscoop and carefully routing the vacuum lines through the split line valley in the airscoop.