I am in the middle of installing a Zex nitrous system in my car and only plan on a 50 hp shot it says buy 2 steps colder plugs any help would be appreciated

 

I honestly went with the NGK iridium 8's, they are about 45 bucks at pep boys and have worked fine with my 55 and 75 shot... the biggest thing you should concern your self with would be the temp of the bottle and keeping it right around 92 degrees so you can keep that perfect spray and at 950-1100 psi.

 

I would definitely go with colder plugs, Be sure they are gapped correctly as well.

 

What size should the gap be

 

Don't know about the Scion, I'm sure a quick search should get you the correct number. Probably around .44