I would like to hear from people what benifits they have experienced from installing the Helix Spacer and 80mm Throttle Body on the Boss 290 motors please.

It's worth it, but you're better off starting with breathing mods first (exhaust/extractors/cai). The other bits you mention might be worth a few tenths on a quarter mile if you're lucky.

I have a lot of trouble understanding how this helix spacer can increase power can someone explain i just dont get the creating turbulence in the manifold? anyone fitted one on a dyno?