The only one I know of is the B&M ShiftPlus, which is similar to the one for the 4L60E, 4L80E and the shifts are noticable quicker and firmer. All it take is if I remember right is 3 wires a hot, ground and splice into one wire to the ECM. It has a rocker switch you mount on the dash and the middle postion is off (normal no differance than stock) one way for lite shift and the other way for full shift improvement. Summit has them for $43 part #BMM-70383 here what they say:
Upgrade the performance of your electronic automatic transmission in minutes.
Buick/Chevrolet/Ford/Mazda/Oldsmobile/Pontiac: GM 4T60E, TH350, TH400 transmission; Ford C4, C6, A4LD transmission, ShiftPlus shift improver
B&M's ShiftPlus shift improver systems improve the characteristics of your transmission and let you change the settings as you drive. Great for performance, towing, and RV use, the ShiftPlus simply recalibrates your transmission's hydraulic system through the modular circuit to give you a firmer, quicker shift for better performance and longer transmission life. Installs in minutes with a few simple hand tools.