does anyone know if the is a diffrance between a zetec turbo silvertop and a zetec turbo blacktop.

im planing on doing a zetec turbo for my xr2i and im not sure on what 1 to go for,

i have seen many zt silvertops but not that many blacktops.is this because silvertops are more stronger (definaly cheaper to buy).

a zvh has gone out of my head now and am gonna crack on with the zt but i dont know wot 1 to get.

any ideas?

Thanks,Andy