First thing I would do is run some Octane Booster through the gas tank after a fill-up. It can help with engine knock. It did on mine at least. Maybe a month after that, run Seafoam through the gas tank, brake booster/vacuum line, and oil (but change oil shortly after).
+1^ Seafoam the upper intake and spark plugs have always eliminated that for me. Now a ways over 200k miles.