Go ahead and turn the HSN in and keep the engine temeps at 220 to 250degrees F; this is the operating temps for a F4.1 or K4.6 engine. More importantly, listen to the sound of the engine; when you have the engine tuned for performance and a good idle with excellent acceleration, remember the sounds. Thoe engine sounds are also a major tool to tell you if the engine is in tune. Temps can sometimes lie to you.