According to NGK's website you can use either BKR6E-11, PFR6G-11 plats or IFR6E11 iridium spark plugs for our cars.

Take a look at my post NGK PLUGS!!! see why I think that the iridiums may work.

Lastly, why do everyone call BKR6E-11 coppers? They are no more copper than the plats or iridiums. All 3 plugs have a copper core with different different firing electrodes.

 

I tried iridium once and they do work fine. They're more difficult to gap though, but I personally didn't really see any benefit over coppers. I would avoid platinum plugs, you can use them, a decent amount of boosted cars do, but you have a greater chance of preignition with little added benefit.