After searching through the fourm I have determined that you should run a colder plug if you have a turbo... but.... i'm fully stock.

I have a 2003 TS (2.5L NA) and it's due for a spark plug change. The manual says that I could use a NGK BKR6e-11 OR BKR5E-11.

If it makes any difference the car is driven in BC where we have a faily mild climate (high of 32-35 deg C in the summer and hovering around 20 deg C most of the year). The car is a daily driver and is not taken to the track.

Is one of the plugs more preferiable to the other? What plug comes stock in the subaru?

Read the sticky at the top of this forum, it should have all the answers you seek.

I have looked over the spark-plug faq... and unless I missed something ovious the closest thing I could find to an answer was a screenshot of the service manual stating that either plug would work.

What i'm curious is that if one plug is better/more suited for my use than the other. Seeing how people are only changing their plugs by a degree for ever 75-100hp (and the ts only has 165hp stock) they add... one step in tempture does seem like a big deal.

Since your car is stock, use the plugs recomended, there is a reason why they are in there from the factory, there will be no benifit to using a different plug.

.....well.....I'd buy one set of each.....as they are ~$2.50 each.....and when you take the ones that are in it, OUT....just put what was IN it BACK in and take the other's back to where you bought them and exchange them for another set of what you need for the next change.....and done.