valve timing
Are you sure about that? Loosening the valve lash makes the cam seem smaller, which helps bottom end performance. Tightening makes rthe cam seem larger, which helps the top end. That has been my experience.
If you play with lash up to .004 looser and tighter, you may find minor improvement. It will also tell you if cam you have is too large or small if it wants lash set different than factory setting. I set lash .006" tighter cold than hot specs for BBC with aluminum heads and iron block.