Broken plugs are more common on the 3 valves and there is actually a specific tool to get broken plugs out. They break on removal from being in too tight. The issues we have are the PI heads with the very few threads for the plugs to grab onto.
Just make damn sure you do NOT crossthread a plug on the way in, use anti seize on the plug threads and tighten them to spec with a torque wrench.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.