A semi-implicit operator splitting has been developed to treat collisions in the electromagnetic version of the GYRO code. Recently (as reported at the recent Sherwood Theory Meeting in Rochester), collisionless GYRO simulations of DIII-D L-mode discharges reproduced the experimental rho_star scaling, but overestimated the absolute value of transport by about a factor of 2.7. New collisional simulations reduce this overshoot to only 1.7. This is the first time a comprehensive gyrokinetic simulation has been matched so closely with experimental data. This is a milestone for gyrokinetic research.