Spray in the engine bay, not the resonator (the big white box in fender well, which is before filter, even it is leaking, the water u spray will be stopped by the air filter, nothing would happen). Spray on the hoses from the big black box all the way to ur intercooler.

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MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport