I have a 2005 Mustang GT with a zex nitrous kit. I also have a diablo predator. I've been running at 125hp shot with no problems. I have ford racing sparkplugs (2 step colder). I decided to go with a 150hp shot and burnt 5 out of 8 plugs. Should I get a (3 step colder). The shop did all the timing with the diablo.