Well, you've gotten your answer to your codes. EGR flow too low; coolant temp sensor, interval too long, and air mass meter. The only one that will leave your fanny stranded is the air mass meter. It is directly behind the air filter box, I would try unplugging it and plugging it back in. The coolant temp sensor interval too long, will make you use a bit too much gas in the first 15 minutes or so driving. It simply means as far as your car is concerned it is taking an incredibly long amount of time to warm up. This could be a stuck open thermostat, the ECT sensor, or a combination thereof. This can strand you only if it has been going on for quite some time, resulting in fuel fouled plugs....but again...I'd be opting for the air mass meter. In theory, you can unplug it and go into "limp home" mode, but I've seen 850's fail to limp.

Chris