Recently we published [Liu et al. J. Chem. Phys. 2013, 139, 154312] an analysis of the rotational structure of the (B) over tilde-(X) over tilde origin band spectrum of isopropoxy, which confirmed that the double methyl substitution of methoxy to yield the isopropoxy radical only slightly lifted the degeneracy of the formers (X) over tilde E-2 state. Additionally the spectral results provided considerable insight into the relativistic and nonrelativistic contributions to the experimental splitting between the components of the E-2 state. However, left unexplained was how the Jahn-Teller (JT) vibronic coupling terms within methoxys E-2 state manifest themselves as pseudo-Jahn-Teller (pJT) vibronic coupling between the (A) over tilde (2)A" and (X) over tilde (2)A' levels of isopropoxy. To cast additional light on this subject we have obtained new isopropoxy spectra and assigned a number of weak, forbidden vibronic transitions in the (B) over tilde-(X) over tilde spectrum using new electronic structure calculations and rotational contour analyses. The mechanisms that provide the nonzero probability for these transitions shed considerable information on pJT, spin-orbit, and Coriolis coupling between the (A) over tilde and (X) over tilde states. We also report a novel mechanism caused by pJT coupling that yields excitation probability to the (B) over tilde state dependent upon the permanent dipole moments in the (B) over tilde and (A) over tilde or (X) over tilde states. By combining a new (B) over tilde-(A) over tilde and the earlier (B) over tilde-(X) over tilde rotational analyses we determine a much improved value for the experimental (A) over tilde-(X) over tilde separation.