3000gt w/ erratic idle need help

Intermentint problem sometimes starts and runs fine, sometime will not idle on cold start. Mostly does it when at running temp. Wants to die alot while shifting and sitting a red lights. No power loss, no check engine light. Always worked on by dealership. Has anyone had this problem and if so please help. Thanks.

Spark plugs and spark plug wires.
 
Change them.