check engine light flashes, no codes reading?

[NissanRWD]

I have a 96 5 speed with 125k. My check engine light flashes on and off randomly. The code came up for the camshaft position sensor. P304i think, or P340. I remember having to figure out if it was camshaft position or crankshaft. Anyway I was going to pass smog but then they said my timing was off. So we fixed that and now there's no code coming up but the check engine still flashes randomly. The car runs fine. It's all stock. Only things I can mention is together previous owner had the revs 1000 for some reason. Im 99% sure it's not an auto swap. He told me the code he pulled up before was the egr valve but that never came up since he said he saw it. I just need to pass the visual inspection for another my check engine keeps coming. I don't wanna pay over 100 just to pass a visual inspection under the table. We've reset the computer and battery and it still keeps coming up with no codes and flashes. Any ideas? Bad ecu? Its not a cylinder misfire either cuz the car runs perfect.

If you got a smog guy who can pass visual in orange county, Pm me