Stuck pad pin plug on rear caliper

spary some wd40 on it and let it soak for a bit and try to unscrew it, if the allen head is stripped out relly bad you can try tapping a torx bit in the hole , that trick usually works. You can also try heating around the pin witha propane tourch but thats if all else fails . when you do get it out get some aftermarket pins that use a hex head instead of an allen .