The TV Plunger should be even with the Valvebody when the TV Cable is fully pulled.
You shouldn't have 'any' TV cable slack at Idle.
What TV cable Bracket and Geometry corrector are you using?
Disconnect the TV cable, Engine idling, pull the TV cable out a dozen or so times & let it snap back. May clear any trash, sticking/binding TV or TV plunger.
Now try to readjust the TV cable.
Scroll down to where the 'Red' writing starts. Paragraphs 1-9, there're 3 Pics between 5-6: