If anyone uses this I would be surprised if they tell anyone. My first project using my 3d Printer to try and see the limitations of the slicer before having to open up something better suited for the task. Printed with pla and haven't seen any deformations due to heat.

2 GFB style trumpets both will fit the factory BOV on the GT models up twin turbo stinger

Large Trumpet: its a press fit over the factory BOVs Lip. Can be a little wonky so I use a rubber O Ring in the back of the BOV to keep it from moving. Will not make a whistling noise.

Small Trumpet: Does Whistle, fits the interior of the factory BOV, honestly looks weird and may pop out while driving

You can nestle the small trumpet in to the large which I feel is the best of both worlds but the small trumpet will need to be glued/affixed in place to keep it from popping out.

Reworked: GFB Turbo Blow Off Valve Trumpet Whistle Respons https://www.thingiverse.com/thing:2734126