I'm pretty sure I remember a story about Chevy voiding a camaro owner warranty b/c of a catch can... don't have time to google it now... I'd have a hard time believing Ford would void a GT350 warranty for this, but I guess you never know.
I'm in Danville - happy to take you for a ride in my GT350R, but it's really not close to what my normal GT350 was... highly recommend going for a ride in a nonR.