VERY common problem I found with my 3T. Even new gaskets if not aligned and installed just right would leak like yours is.
Look up Stewart Wilkins Motorsport he carrys gaskets.
A new one will fix the problem, just make sure when you install it that it doesn't slide around and move and stop sealing.
The original Toyota ones I found better as they had little tags to hold it in place better.
Cheers
Joel
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