code 32 on 1992 gmc diesel

my check engine light came on and i triped my comp. with my gm key and it
gave a code 32 wich in my repair book (haynes) it means egr circuit fault
i checked the vac pump and i have about 25 inch vac.then the vac line goes
into a set of solenoids there are three then there is a hose comming out
of one solenoid that splits one hose goes th egr and one goes to map
sensor i pulled the hose off the egr and i have 14-16 inches of vac. my
egr works with it running the egr is open all the way up and when i rev up
the engine it snaps closed. now here comes the strange part the check
engine light is on and if i up the engine rpms the engine light goes out
if i drive it the light comes on and off if i stop the light comes on if i
take off the light will go off for a few seconds then come back on. if i
pull the line off the egr and plug it the light goes out i also checked
for bad vac hoses and didnt find any i am lost on this one. also if any
one has a web sight that has a vac diogram that has these solenoids in it
please let me know thanks

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