My dilemma is that I just picked my S up. 05 with 35k on it. I want to change the plugs, peace of mind sort of thing, especially since the air filter was as dirty as it was

It doesn't have a pulley yet, but should be getting one within the next couple months depending on when I have the time to install it.

Should I just wait to change the plugs till the pulley goes on?
Replace with OEM and change again when the pulley goes on?
Or put on colder plugs like the IK22 in anticipation of the pulley?

Are the Densos the best plugs to be running? I have read a lot about the NGKs too. Just preference? What about numbers for stock/colder?

 

With only 35K on the OEM plugs, I'd wait for the pulley. OE plugs should be good for at least 50K. Many don't bother to go with colder plugs with the 15% pulley but, I did upgrade to the IK22s when I did my 15%. The first ones lasted 20K miles with no problems. Currently running second set.
You may want to pull the OE plugs to take a look at their condition. When you re-install use a small dab of antiseize and torque to 18 ft.lbs.

 

Get a set of iridium NGK IK22's. You can install them when ever you feel like before or after the pulley swap. Go with NGK's as they seem to be less prone to back out of the engine. What my big question is. Do you have an intake on. If you do not, put in an intake before you swap the pulley, as your car will starve for air breathing from the stock intake. You'll notice it at high rpm's the car will seem like it cuts out of chug/lug a bit.

 

apex - It's a preowned car, I don't know what was run for gas, and know that it must have been starving for air through the dirty as anything filter.



The flash made it look a lot better than it really was.

I don't have the intake yet, I was planning on doing the intake/pulley/one ball all in one shot. I've heard the same thing about the NGKs not backing out as much vs. the Densos, I'll have to pick a set up.