We present computer simulations of entangled finitely extensible worm like chains, including real space chain coupling, in shearing flows, Extending existing simulation techniques, we examine the microstructure of such concentrated polymer systems at both equilibrium and in "Fast" shear flows and compare our simulation results with experimental single molecule data for DNA and with bulk rheological measurements. At equilibrium we verify that our Simulation technique predicts that the longest relaxation time of the system scales as the number of entanglements to the 3.4 power. Time traces of polymer conformation near equilibrium show fluctuations not only in the flow and gradient directions but also in the vorticity direction as well. At stronger flow rates, we demonstrate the existence of large stretching in the flow-gradient plane coupled to rotational fluctuations which result in polymer tumbling. Under such nonequilibrium flows, we find excellent agreement with single molecule data with regard to the configurational variability of individual molecules for (gamma) over dot tau(R) <= 5. Both experiments and our simulation data show that chain extension exhibits a wide range of values with maximum extension exceeding 40%. Furthermore, histograms of chain orientation, measured via simulations, are symmetric around 45 degrees and then become skewed toward 0 degrees as the flow strength is increased. However, even under relatively fast flows, the average angle decreases only modestly, and thus strong alignment is never observed. Also in agreement with single molecule data is Our simulated variation of the power spectral density of chain size projected in the flow direction, which decays as omega(m) where m similar to -15 and m = -2 for slow and fast flows, respectively. Finally, Our simulations are able to predict the onset of a plateau in shear stress for tau(-1)(D) < (gamma) over dot < tau(-1)(R) and also a dip in the linear viscoelastic loss modulus at intermediate frequencies, both classic signatures of entanglement. Our shear stress results are in quantitative agreement with experimental rheological data for T4-DNA. We find that the size of the polymer in the flow and the gradient directions are relatively constant in the range of now rates corresponding to the shear stress plateau. Only upon the imposition of higher shear rates, when the shear stresses exhibit an upturn after the plateau, do the two size measures display significant variations. These "frozen" changes in the size and orientation of the chains are the microscale cause of the shear stress plateau in our Simulations,