In general correlated models , in addition to the usual adiabatic component with a spectral index n _ { ad 1 } there is another adiabatic component with a spectral index n _ { ad 2 } generated by entropy perturbation during inflation .
We extend the analysis of a correlated mixture of adiabatic and isocurvature CMB fluctuations of the wmap group , who set the two adiabatic spectral indices equal .
Allowing n _ { ad 1 } and n _ { ad 2 } to vary independently we find that the wmap data favor models where the two adiabatic components have opposite spectral tilts .
Using the wmap data only , the 2 \sigma upper bound for the isocurvature fraction f _ { iso } of the initial power spectrum at k _ { 0 } = 0.05 Mpc ^ { -1 } increases somewhat , e.g. , from 0.76 of n _ { ad 2 } = n _ { ad 1 } models to 0.84 with a prior n _ { iso } < 1.84 for the isocurvature spectral index .
We also comment on a possible degeneration between the correlation component and the optical depth \tau .
Moreover , the measured low quadrupole in the TT angular power could be achieved by a strong negative correlation , but then one needs a large \tau to fit the TE spectrum .