We have made several improvements to BBSIM, a parallel beam dynamics simulation code. These include the addition of diffusion characterization routines, dynamic changes in RF frequency, accurate modeling of beam transfer function measurements, ac dipole, single kick measurements and the effects of resistive wall wake fields. These improvements are in the process of being benchmarked against measurements in the Tevatron and RHIC and are being used to better understand the complex interaction of chromaticity and wakefields on chromaticity measurements in the Tevatron, RHIC and LHC as well reveal the character of diffusion in these machines.