M103 EGR Fault Codes

[Motor Head]

My 1990 300 SEL kept registering an EGR fault on the computer. I checked the valve with a Mity-vac and the diaphram was definitely leaking. I checked the new one before installation and it held vacuum fine. After 3-4 weeks of driving I have the same fault code (16) again. What other areas can I check that would cause the car not to get EGR when it was suppose to? I am assuming that whatever it is that checks for EGR under the necessary conditions is working properly.

Thanks for the help,
Motorhead