Does anyone know if the 6th gen exhaust manifolds are prone to cracking. Or even any kind of problem in that area (manifold gasket, gasket to downpipe, etc.) I am still trying to track down a 420 code that has taken over my life. At this point I really don't feel like its the cat. We hooked the computer up and the O2 sensor response on the primary was not fluctuating the way I understand it should. kinda sluggish. we also put it up on a lift to get a good look, but couldn't see any telltale blacking from exhaust leaks. Actually, I was surprised that the condition was pretty good under there. TIA

 

Mines hasn't crack for 140,000 miles. And I've taken my car to the race track (Willow Springs) and the drag strip (Irwindale 8th mile). With the heat shield off too.