gSlider is an SNR-efficient simultaneous multi-slab acquisition that has shown great potential for high-resolution diffusion imaging (DI). In this work, approaches to improve the fidelity of gSlider are proposed. A modified reconstruction which incorporates B1+ inhomogeneity and T1 recovery information was developed and demonstrated to successfully mitigate slab-boundary artifacts in short-TR gSlider acquisitions. Slice-by-slice B0-shimming through multi-coil shim-array, and high in-plane acceleration through virtual-coil GRAPPA were also incorporated into the acquisition and demonstrated to achieve 8-11x reduction in B0 distortion in single-shot EPI. The modified gSlider acquisition/reconstruction was used to acquire high-fidelity whole-brain 1mm isotropic DI with 64 diffusion-directions in 20-minutes at 3T.