Maggy, my suggestion was to find out if your van has "bulb out" detetection or not. If it doesn't, then no need for special wiring. Mine doesn't have this feature, I put a 35W HID conversion on Hi beam only, and no errors (BTW hi beam conversions are legal in my State as long as I don't alter Lo beam).
The only way you will know for sure if yours will object to a 35W load or not is to put a 35W load in place of your 55W globe. Maybe find a 35W globe and jury rig that into the std circuit to see what will happen ?
bvm, The Osram Nightbreakers are 55W (same as std). I tried them (as well as Philips X-treme and the Osram 65W Rallye bulbs).
The Nightbreakers are nowhere near a real 90% improvement over std globes, I'd say more like 25-30% better (still a worthwhile improvement, but not what they claim).
I preferred the X-treme globes to the Nightbreakers for output (by a small margin), and the Nightbreakers have a bit of a reputation for short life (IIRC there are some posts around about it). The Nightbreakers are slightly "whiter" than the X-treme (they have a blue filter on the glass) if that is important to you.
I haven't heard of anyone haveing problems with the extra current draw of the 65W globes, and they were more like a 40-50% improvement over std.