Toyota Repair: 1999 Camry Check Engine Light P0401, haynes manual, egr valve

Question
The check engine light came on in my 1999 Camry 4cyl 2.2l will 75000miles automatic. The code is P0401 insuffiecient EGR flow.  I have tested the EGR valve per the Haynes manual and it tests OK.  I also have taken it off and cleaned it.  I cleared the code and it comes back.  What are some other causes and options. Thanks

Answer
The most common problems are the EGR modulator valve, it's right next to the EGR valve, and the EGR vacuum switching valve(VSV) remove the modualtor valve and see if air passes from the bottom port through the valve , if it does replace the modulator.