I still wonder if the exhaust behind the manifolds might have something to do with the broken manifold bolts.It's always the rear ones that break,and that's where most of the exhaust weight would be located.Only thinking this,because the 5.7 cars use basically the same cast iron log manifold,and they don't break the back bolts anywhere near as much as the trucks do,and they don't use a mid pipe like the trucks do,or hang as much weight off the manifolds with their dual pipe set-up , that runs to a X crossover quite aways back of the cats.
If it was strictly expansion/contraction breaking the bolts,or mds kicking in,you'd think the trucks would break the middle bolts instead of always breaking the back bolts.The cars also cycle the same cylinders in mds mode,and don't break the back bolts.
The basic differance between the cars and trucks are the midpipe / midpipes on the cars
