  We give the decomposition into irreducible factors of Weil representations of
the symplectic groups at even levels, generalizing previous decompositions at
odd levels. We then derive the decomposition of the quantum representations of
SL2(Z) arising in the SU(2) and SO(3) TQFTs. As application we show that, when
the level indexing the TQFT is not a multiple of 4, the universal construction
applied to a cobordism category without framed links leads to the same TQFT.
