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They are all both
SMPI refers to the firing order & location of the injectors
MDS refers to the dropping of 4 cylinders for economy
VVT refers to the variable valve timing which gives the effect of a larger cam @ higher RPM
and every Hemi these days has all 3 features
Well, every 5.7 hemi these days...........I think the bigger hemis (6.1 & 6.4) have the SMPI & VVT but not the MDS, and the 6.2 in the hellcat, well, it's just bad to the bone.......................