^^^Well it
would have been the promised, but undelivered, 3" Tomei titanium system, but since it seems that they have abandoned us PERMANENTLY, I'm not sure which of the stainless systems are the most featherweight.
One also must consider the system's SIZE in tubing diameter, since that directly effects the mass, and it is pomegranates to broccoli to compare the weights of a 2.25"/2.5" system to a 3" system.