You asked, we delivered. Many times we have been asked for a replacement trumpet that gives a different sound, and here it is. Simply screw this trumpet into any Stealth FX and it will produce an aggressive whistle that sets your car apart from others. In normal driving conditions it gives a typical “whoosh” sound, but once the revs and boost level rise, a high pitch whistle noise takes over. 5701 Whistling trumpet drive-by Stealth FX with the new whistling trumpet, 15psi boost on a WRX, recorded from the side of the road. 5701 Whistling trumpet in-car Stealth FX with the new whistling trumpet, 15psi boost on a WRX, recorded from inside the car. Note that there are a few conditions that must be fulfilled to get the most out of this product. Your Stealth FX should be set to full atmosphere venting, and boost must be at least 12 psi (0.81 bar). The whistle noise is dependant on air velocity through the trumpet, and low-boost set-ups will not be effective. The Stealth FX is available for: Subaru WRX, Nissan 200SX, Nissan Skyline and Universal Fit.