dignosing this problem right now on the 99 camry 2.2L inline 4cyl
the EGR valve seems to be working (runs rough when apply vacuum to the 1 port) but the vacuum doesnt hold like it says it should (leak in a diaphram plunger internally???) and the ... the ... the thing that sits right next to the EGR valve ... name is escaping me right now ..., that seems to have air flowing normally through it in one direction anyway. I didnt spend a lot of time trying to determine if it was resisting flow at higher RPMs.
New EGR valve is EXPENSIVE. Any shade-tree fix methods?
Two things to note:
-The problem progressively got worse (assumption from the fact that the CEL would come on and go off at longer and longer intervals until now it just remains on all the time).
-One of the vacuum lines in the area of the EGR valve (not sure which one) was completely plugged with carbon/soot dust. I'm in the process of replacing all of them but didnt have enough tubing ... gotta pick some more up.