The 2 Glow plug codes won't put you in limp mode. Looks like the 380 code means you need a new glow plug module and clearly 671 means you need a new glow plug. #1 is the closest one to the front of the vehicle. A big drawback to the glow plug module is that if you have glow plug go bad, it blows a non-replaceable fuse in the glow plug module. This means that if you just replace the glow plug, it won't work. You will have to replace the glow plug module, too. There are two fixes to this- one is Bill's Glow Plug Mod- search the forum for it. Bill basically took apart his old glow plug module and soldered in replaceable fuses. There's also a newer style glow plug module that has automatically resetting fuses, so if a glow plug dies, you don't loose the module, too.
The last code, 299, is what put the OP in limp mode. Underboost means that there is a leak in the turbo system plumbing. Maybe a cracked turbo resonator or a spit hose. Or, if you are lucky, just a loose hose clamp. Search the forum for ways to find the leak, but a good one is to have a helper put the van in gear, step on the brake and the accelerator and you stick your head under the hood and listen for the whistling or blowing from the crack.
Good luck!