it happens when your accelerating, it never happens when cruising at 60, even 70..and 80+ means it has happened at 80mph before, but usually its around 90-100 it starts. I gotta work so ill try and pull the plugs when i get back. How much do plugs,wires, and coilpacks cost on these cars? (never had a 3800 befrore) Any sparkplug/heatrange you'd recommend for better performance?