P1404 code came back

I have a P1404 code on my 01 GP 3.8l mileage:130k last year. I cleaned it with crab cleaner and the code went away for 2 month, last week this code came back. This time, the crab cleaner doesn't work any more. The check engine light stays continuously so I decide to change a new one. But I search on google and found that several people also have the same code and changing a new EGR valve sometimes dose not solve the problem. Do you guys have any idea on this? I just want to make sure it is necessary to change a new one.
BTW, what is EGR valve gasket used for? I don't have this gasket on my car

It is very common for the EGR valve to go bad especially with 130k on the clock. I wouldn't be scared to put a new one on there. It is extremely rare for a wiring problem or PCM problem to occur. If there isn't an EGR gasket between the valve and it's mating surface, you WILL have a nasty vacuum leak and an exhaust leak when the valve is open. You have one and you will see it when you take the EGR valve off.

With this DTC the PCM is detecting that the actual EGR pintle position is not at the desired position. In other words the EGR may be staying open when commanded to be closed which will set the DTC.

Due to the cost of the EGR valve it is best to make sure the 12 volts for the EGR solenoid and the PCM 5 volt reference signal are good just in case. That can be checked with a multimter (DMM) at the EGR electrical connector. Pin E 12 volts at ignition to on and 5 volt ref signal at Pin D.