I have had the check engine light on my car(1998 Toyota Camry 4cyl 2.2L) for a while now, and just recently I decided to take the time to fix things up. So I bough a code reader and got P0401 which is EGR Insufficient. I reset it just for the heck of it. About 20 miles later it came back on. Then I did and lot of research and read dozens of post and now I am stuck and in need of some help. So first I cleaned out the EGR valve with some carb cleaner and replaced the gasket. I reset the code and then about 20 miles later the light came back on. Then I inspected the EGR modulator. The filter was not very dirty at all, there was just one small dark black spot. After some more research I found that the Vacuum Switch Valve was a common problem and so I went ahead and replaced the part with a new one. I reset the code, but then the weird thing was that the check engine light came on within 10 secs. I reset it again and came up with the same result. So I guess my question is why would replacing the EGR VSV cause my check engine light to come on sooner than it did before? Also, does a small dark spot on the modulator mean it needs to be replaced(one guy posted that it did)? Any help, suggestions, or past experiences would be great. Thank you.