  We give arguments for a conjecture made in a previous paper, that one has to
use only the gauged sugra action for the calculation of correlators of certain
operators via the AdS-CFT correspondence. The existence of consistent
truncations implies that the massive modes decouple, and gauged supergravity is
sufficient for computing n-point functions of CFT operators coupled to the
massless (sugra) sector. The action obtained from the linear ansatz, of the
type $\phi(x,y)=\phi_I(x)Y^I(y)$ gives only part of the gauged sugra. This
means that there is a difference for the correlators on the boundary of AdS
space. We find, studying examples of correlators, that the right prescription
is to use the full gauged sugra, which implies using the full nonlinear KK
ansatz. To this purpose, we analyze 3 point functions of various gauge fields
in 5 and 7 dimensions, and the R-current anomaly in the corresponding CFT. We
also show that the nonlinear rotation in the tower of scalar fields of Lee et
al., Corrado et al. and Bastianelli and Zucchini produces a consistent
truncation to the massless level and coincides with the Taylor expansion of the
nonlinear KK ansatz in massless scalar fluctuations. Finally, we speculate
about the way to do the full nonlinear rotation for the massive tower.
