Here,s something that also help. Vaccum lines may look and feel good, but they ma have an internal failure that will cause a problem. This is a failure similar to that of a hydraulic brake hose.
Another thing is the carb base gasket,it can deteriorate on the inside edges. This can cause minute peices of the gasket to get in to the carb, as well as cause fractures that lead to leaks.
As far as egr problems go, unplug the valve and check to see if the diaphram moves manualy.
If it moves and the hose looks and feels ok [refer to example ] above.
***** Warning this is unfortunately a true story***** I was at a shop in Beaver County Pa, and saw a man diagnos a car with a bad egr he sent a kid to go get a wooden box full of used egrs. He rooted around came up with one and slapped it on. He had an old drill with a length of transmission cable chucked in it, and was cleaning old egr valves.
I dont condone this practic
Thanks,Benamcfan.