No problems with mine so far. I have a 700 Watt stereo system and have no undercharging problems. Since I never ran my A/C before installing the pulleys, I'm not sure how they affect that. But, there is definitely a power loss when I kick on the A/C.
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'96 GT
5-speed,K&N air filter,Roush Cold Air kit,80mm MAF,Mac Cat-Back,Mac Pro Chamber H-Pipe, FMS 3.73's, FMS 70mm TB, Steeda Tri-ax, March U/D pulleys
T-Bone's '96 GT