I've got 2 sets of 4age velocity stacks (trumpet) to let go,
no brand, locally made, can install in air surge tank replacing old stacks,see attachment.
RM120 each set-SOLD OUT!!
I made one myself at home ,
i think it works not bad ,
material = plastic bottle , gas hose < i'am using 9mm transparent type > and sponge like thing that you often get when buying delicate items like computer...