The gasket I have found that fits and works best for me with the TA valve covers is the Victor Reintz VS39763 which is a cork gasket.
If you use a light spray of adhesive on the gasket and VC and let it sit for a few minutes, it will stay in place during the install, and you can R&R the cover with the same gasket a few times if needed.
Do NOT over-tighten the bolts during the installation, do it in stages 10-15 minutes apart until you feel no more gasket compression.
Also, check that the bolts do not bottom out before proper compression of the gasket is reached, and I have found some holes are too shallow and washers under the bolt heads may be needed?
This is common on an alum head, not so much on the iron heads.
