I have a really strange issue with a new to me IO540-D4A5 engine. It has a lightspeed on the right and a slick on the left. When we did the first conditional inspection it appeared to be timed at 20 degrees retarded. I dont see how it could have even ran at that setting. I pulled the mag and it looked fine but had a weak spring on the impulse mechanism. I sent the mag off to have the 500 hr inspection done. I bench tested it and it was fine and sparked on all cylinders. Someone had set it for right instead of left turn. We changed it to left hand and set it to 20 degrees advanced and it was not happy. There was no indication of an issue in the log books and no mention of a relocated timing mark. It was running fine before the inspection but I did notice the Tempest fine wire plugs electrodes were brittle and broke off when the gap was checked? I guess Ill see when we install the mag how it turns out. Never seen this before and there are multiple notes of the mag timing being checked. It has 575 hrs total time and according to the logs it was replaced at 212 hrs by the original builder but no mention of any problems