If the vacuum hoses don't fix your problem, you probably have a plugged EGR tube from the EGR valve to the intake manifold. This tube plugs up with carbon over time and causes the EGR flow to be reduced to the point where it is essentially inoperative. You will want to replace the EGR tube (you will need to R&R the intake manifold). The tube can be cleaned out with a speedometer cable on a drill but this seems to have limited success. As you can tell, this is a common problem.