Metzler has their own recommended tire pressures listed in their literature and on their website. On some tires they have a significantly higher inflation pressure recommendation when compared to the stock Dunlops, but you need to make sure you use the figures for the specific tire you're using. For instance, the alpha designated tires (letter sizes like MU) use the same pressures as stock. But the metric (ie. 140/85) designated 880's use a significantly higher pressure. In the attachment, note the differences in the first two sections, and then the special note for certain sizes in the third section. Click on the attachment to blow it up to full size btw.
Jerry
edit: Metz lists their pressures as the minimum pressure in the tables, rather than the industry standard method of listing recommended cold inflation pressures. Semantics perhaps, but it also leaves them a big out when folks complain about wear or other issues. "Oh, you should be running higher pressures and that wouldn't happen" is something I've seen a lot of people claim they were told when they complained about high rates of wear. My feeling is if they really want you to run 44 psi instead of 40, they should spell it out in the charts and not just through word of mouth that can be easily denied later.
Anyhow, somewhere between the number in the chart and the maximum inflation pressure molded into the sidewall is an optimum figure. Personally, I'd probably shoot for something halfway between those two numbers and see how that works.