so i noticed a drastically changed exhaust note during my last flight of the Fun51 with a ST GS .45 on it this weekend. I landed immediately. inspection revealed that the header broke the front attach lug off where it bolts to the head. the engine was not running lean at the time (it might have gone lean after it broke for the 30 seconds or so it took to get it down). the header is like $11, so no big deal, just curious if anyone has any suggestions why it would break there? It has lots of hours of run time on it as well as the fact that i was dogfighting with an imaginary foe at the time. so what do ya'll think, just metal fatigue due to countless heat cycles? maybe me yanking the plane all over the sky contributed? just looking for some theories.

thanks.