unfortunately, spark plug marketing has really driven a falsely based frenzy around gaining power from spark plugs. Their function is to basically pass a high voltage arc in a highly volitile compressed environment to cause an explosion. Unless the electrodes are extremely worn/resistive, or the gap is incorrect, there isn't a whole lot that the plug can do. Bosch has alway been a high quality plug, and their platinum plugs offer a long lasting option as the electrode does not wear as fast (we're talking after 20 or 30K miles of usage). The multiple prong plugs like bosch platinum+4's are really wasted on good running engines, because only one of the tabs can possibly fire at one time (if all four were able to carry the arc, it would diminish the effect of the spark). so having a +4 type of plug would only really benefit someone whose engine was fouling plugs pretty badly...probably not a recent volvo with less than 200k miles.

Stick with what the factory put in, or maybe go with bosch regular platinums...you won't really notice any difference except when they fail (rarely).