if you have a lot of miles on the van, definiteyl clean the EGR ports. it's not tough to do, and it can cause a lot of problems making the engine run rough.
check all your vaccum lines while you're in there. if any of the lines or hoses look cracked or dry rotted, replace them. an easy way to check for leaks too is to spray some starting fluid or WD-40 or something flammable on the vacuum lines while the engine is running, and if it causes the engine to rev up then you have a leak. just be careful where you spray since it is flammable.
if you clean the EGR ports, i'd also change the #1,2, and 3 spark plugs since you'll have the cowling and the upper manifold off, giving you some room to work with. | 
