GFB Whistling Trumpet for GFB Response/Deceptor Pro BOV Black - Suits High BoostGFB Whistling Trumpet You asked, we delivered. Many times we have been asked for a replacement trumpet that gives a different sound, and here it is. The ability to change the sound of a blow off valve is increasingly becoming an important issue with buyers, who want to sound different from everyone else. In 2004, the Whistling Trumpet was released which emitted a piercing screech when driving aggressively. The 5701 can be used in place of the standard