buy a petit aluminum ast ( air seperator tank ) basically it's like a coolant resivoir. those cars are easy to make fast but hard to keep cool, before i did hp mods i'd first get a better radiator. on some forums you'll see people say to run all the same plugs....my bro tried that on his fd and it fouled em out. Mazda designed the car to run with these plugs for leading and these plugs for trailing for a reason. when you start messing with shit that doesn't make sense to you....you're bound to have problems. buy a set of plugs and wires and make sure you don't put em back together backwards or upside down etc ( a lot of people do that ). then buy an extra set of plugs and always keep em in the glove box with the sockets you need to change em on the fly whatever you do don't half ass the car. besides the ast, radiator, plugs and wires, whatever else you do to the car have all the parts all at once and get it professionally tuned right away. my bro still got $9500 for his fd with a chipped apex seal though LOL. so if you fuck up your car it's still worth some money HAHAHA.