What can I do to maintain a consistent idle for more than 15 seconds? Ive tried every single needle adjustment...nothing. Right now I have ODonnell Medium Sport Plugs and when I finish with them (2 left) I want to try something else. I will be running Byron's 30% Pro Driver in the Mach 427. Ive heard soem people say to run cold plugs and 30% on this engine in previous threads, but I want to get a second opinion. Which plugs will be better for idling/durability? And what is the difference between the ODonnell sport and say the #99 cold plug?