i got 0302, after i cleaned my egr valve, pipe, i got this code everyday(before clean it, it was one time by week. I check the EGR valve and it seems to work fine, no air leak, etc.

Do you think this happen because the EGR valve after cleaned i didnt put the gascket?(i dont have anything to replace it, just hight temp silicone)

Anyway, do you know how much do i have to pay for a new egr valve? and where???