  Charmless B decay modes $B \to \pi \pi, \pi K$ and $KK$ aresystematically
investigated with and without flavor SU(3) symmetry. Independent analyses on
$\pi \pi$ and $\pi K$ modes both favor a large ratio between color-suppressed
tree ($C$) and tree ($T)$ diagram, which suggests that they are more likely to
originate from long distance effects. The sizes of QCD penguin diagrams
extracted individually from $\pi\pi$, $\pi K$ and $KK$ modes are found to
follow a pattern of SU(3) breaking in agreement with the naive factorization
estimates. Global fits to these modes are done under various scenarios of
SU(3)relations. The results show good determinations of weak phase $\gamma$ in
consistency with the Standard Model (SM), but a large electro-weak penguin
$(P_{\tmop{EW}})$ relative to $T + C$ with a large relative strong phase are
favored, which requires an big enhancement of color suppressed electro-weak
penguin ($P_{\tmop{EW}}^C$) compatible in size but destructively interfering
with $P_{\tmop{EW}}$ within the SM, or implies new physics. Possibility of
sizable contributions from nonfactorizable diagrams such as $W$-exchange ($E$),
annihilation($A$) and penguin-annihilation diagrams($P_A$) are investigated.
The implications to the branching ratios and CP violations in $K K$modes are
discussed.
