Slightly off topic but has anyone else tried Redline Water Wetter. I tried it in my 335i and the normal running temp went down by 15 degrees. I think that the correct method for this product is to flush out the system so that the wayter wetter is not mixing with other products and then fill with distilled water and water wetter. There have been mixed reviews of this product but it seems to work best with engines that run hot. This may be stating the obvious but the cooler running engines are already efficiently removing heat so the difference isn't as great as something like an N54 which runs quite hot. I'm not an expert on these things so check it out for yourselves.
Also - what about a more efficient intercooler? These are mounted out of the way of the existing radiator so you won't be affecting airflow to it.