I have the same issue with mine. I never run the AC because of the theft of power and the lame idle. I think it is totally normal though. If it isn't causing a stall, it shouldn't be too much of a concern. Any time the AC is turned on, the AC compressor switches on and robs power from the crank, so this seems normal. I would get it checked out by a mechanic to make sure it is normal, though.