  We study the effect of the infrared (IR) geometry on the phenomenology of
warped extra dimensions with gauge and fermion fields in the bulk. We focus in
particular on a "mass gap" metric which is AdS in the ultraviolet, but
asymptotes to flat space in the IR, breaking conformal symmetry. These metrics
can be dialed to approximate well the geometries arising in certain classes of
warped string compactifications. We find, similar to our earlier results on the
Kaluza-Klein (KK) graviton, that these metrics give rise to phenomenologically
significant shifts in the separation of KK gauge modes in the mass spectrum (up
to factors of ~2) and their couplings to IR localized fields (up to factors of
~5-10 increase). We find that, despite shifts in the spectra, the constraint
m_KK > 3 TeV from S remains robust in the class of 5-d mass gap metrics, and
that the change to T is not significant enough to remove the need for custodial
symmetry.
