I have the ngk racing plugs at 1 step colder with a stage 1 tune and I haven't had any noticeable issues on the AP. I figure I'd check them at 10k miles, about 5k to go, and if they look bad I'll think about going back to stock. My concern is that I just do a lot of driving that only lasts about 10-12 minutes, so with my short drives and the colder plugs I'm not sure things are getting as warm as they should. The only thing I've noticed so far is I get a ton of misfires at start up if I try to drive my car before the RPMs calm down. Ed made that sound normal and that I should just wait until the RPMs fall before I start driving, but I never had this problem with either of my other cars I tuned. Now I'm kinda thinking that might be the colder plugs. I haven't seen anyone else with this complaint though.