  The naive time reversal odd (``T-odd'') parton distribution $h_{1}^{\perp}$,
the so-called Boer-Mulders function, for both up ($u$) and down ($d$) quarks is
considered in the diquark spectator model. While the results of different
articles in the literature suggest that the signs of the Boer-Mulders function
in semi-inclusive DIS for both flavors $u$ and $d$ are the same and negative, a
previous calculation in the diquark-spectator model found that
$h_{1}^{\perp(u)}$ and $h_{1}^{\perp(d)}$ have different signs. The flavor
dependence is of significance for the analysis of the azimuthal $\cos(2\phi)$
asymmetries in unpolarized SIDIS and DY-processes, as well as for the overall
physical understanding of the distribution of transversely polarized quarks in
unpolarized nucleons. We find substantial differences with previous work. In
particular we obtain half and first moments of Boer-Mulders function that are
negative over the full range in Bjorken $x$ for both the $u$- and $d$- quarks.
In conjunction with the Collins function we then predict the $\cos(2\phi)$
azimuthal asymmetry for $\pi^{+}$ and $\pi^{-}$ in this framework. We also find
that the Sivers $u$- and $d$- quark are negative and positive respectively. As
a by-product of the formalism, we calculate the chiral-odd but ``T-even''
function $h_{1L}^{\perp}$, which allows us to present a prediction for the
single spin asymmetry $A_{UL}^{\sin(2\phi)}$ for a longitudinally polarized
target in SIDIS.
