15.9 at 89 MPH in a 3200 pound vehicle is about 200 HP.I think your engine has the equipment to go faster but needs fine tuning..The fact that it revs to 5500 says something..
What have you done about dialing in the present cam? Is it 9-1 actual measured compression? Is the quench tight a possible? Proper ring sealing and accurate valve job? what is the ignition total timing?
And as some have found out,a ported head doesn't always mean more power...
