2000 Chevy Blazer have a misfire in 1 still, and the engine

i have changed all plugs and wires, distbutor and roter button, and crossed the t's and dotted the i's for a army and shade tree trained mechanic. however it still has a misfire code for spark plug 1, and a hesitation when acclerating and idleling, it does run alot smoother at 35mph and up. but what else could be causeing the rough ride for me and the engine, also have developed a whirring or mild grinding sound while driving but which does quit instantly when you apply brakes, any advise is welcomed, thank you