I have read here in many threads that most of you use the NGK PFR7B for differents Imprezas, including STI.
I have not found a lot of informations about the fitting for STI7 or 8.

As I want to use colder plugs, will the PFR7B be the best choice ?
A friend says me that he uses PFR7G-11... Don't find anything about those plugs.

Thanks for your answers.

 

The last digit(s) in your part number is the gap size. The heat range is the forth. Therefore the 2 plugs you mentioned have the same heat rating. Refer:

http://www.ngkspark.com.au/

Hope this helps a little,

Adam