P0401 Low EGR Flow. Valve OK, stuck Solenoid replaced How to trouble shoot? on 1996 Ford Ranger

P0401 code. (Actually a Mazda B2300) Checked EGR Valve and replaced stuck modulating solenoid. Vac lines checked good too. What should I be checking, and how? Vehicle runs fine except for the light, but emissions test due at end of month.

Asked by for the 1996 Ford Ranger
possibly clogged EGR passages.
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possibly clogged EGR passages.