My 240D would really pull down when the A/C was running, the trick is to turn off the compressor when you need the extra power. If I came to a stop I'd kick off the compressor until I got back up to speed and re-ingage it. The same rule applied to the rare passing situation on the highway. My 240 is almost 2 tons rolling down the road with a 90HP diesel engine, I expect it to load up when the A/C is on, it's just the nature of the beast. Hardly a factor on my 300 turbo.