Rotec 2800 exhaust failure

[nosubt2]

Landed and on preflight for next leg, I discovered that the exhaust manifold for #3 cylinder had completely burned off and there were holes in the exhaust collector for that section. The engine had only 75 hours since new.
WHY did this happen? Is it because the cylinder ran lean. Have not checked the color of the sparkplugs. Should I preform a compression or leakdown check.
Mark

[yoda]

Something happened to me. This pic is when it started to rust out. Exhaust was manufactured from sub quality metals. Purchased new exhaust from Rotec two years ago and have no issues. Rotec claims it’s a better exhaust.