I've been running the APC 12.25 x 3.75 on my Webra 50s with a Mac header and Tuned pipe. I tried the Brodak Y&O 12x4 on my Aeron. The Brodak clearly out performs the Zinger, even the modified Zinger version. The B Y&O doesn't pull quite as well as the APC 12.25x3.75 but more than makes up for it in response. It definiately has my vote!
Also the B Y&O flexes at high RPM that makes it sound like a big Bolly <COOL!!! >
Kevin