Chiral effective field theory provides nuclear interactions rooted in Quantum Chromodynamics in a systematic and consistent manner. To assess the quality and predictive power of chiral twonucleon (NN) and three-nucleon (3N) interactions, ab initio calculations of a variety of nuclear observables are crucial. However, the inclusion of chiral 3N interactions into exact many-body calculations is demanding and computationally expensive. Recently, we completed a number of key developments which permit ab initio calculations of ground and low-lying excited states of pand sd-shell nuclei with full 3N interactions in the Importance-Truncated No-Core Shell Model using consistent Similarity Renormalization Group transformations of the NN+3N Hamiltonian. The explicit treatment of 3N interactions without approximations allows for first studies of the dependence of nuclear-structure observables on the details of chiral interactions. We present first results of sensitivity studies with respect to variations of the low-energy constants and the chiral cutoff of the chiral 3N interactions. Our results hint at missing operator structures in the leading chiral 3N interactions which seem to be necessary to describe certain excited states in p-shell nuclei properly.