Are you being sarcastic or no? Because the exhaust manifolds are identical. Only the risers are different in H.O. applications...
Base/Powerplus: 3" riser with long runner, mixes wet and exhaust really well
H.O.: 3.5" riser outlet, short runner, better exhaust vapor flow, does not mix water and exhaust as well...
Below, PIC 1 is a HO riser, PIC 2 is base/powerplus riser
riser2.jpg
R029004.jpg