The bosch 4 are a waste of money IMO. There are quite a few people on other BMW forums that complain that the bosch 4's caused more problems than anything.
Spark plugs - NGK BKR6E Less than $2 a plug, and they will work as good if not better than every plug on the market.
Replace a quart of oil with a quart of slick 50. You might want to consider running a slightly heavier weight oil as well. This will help keep the oil from leaking out of the seals as fast.
I would change the oil, and run the slick 50 a little bit before changing the plugs. Changing the plugs should fix your power issues, you could also consider "seafoaming". I've never done it on a 4 cyl, but on a six you just run it thought the brake booster line. "youtube" seafoam BMW