go get a new cap and rotor (NOT at Oreilly auto) and try that. Instead of replacing valve springs and fuel system stuff----its a cheaper experiment !

Again---My car sounded exactly like yours did at the same rpm .

It was a faulty distributor cap ...that was TWO months old ! (junk Oreilly crap )

ask Tboomer-- he's the one that loaned me a new Accel cap at the track.