X51

Installed PSS10s on my 2002 C2 996 along with GT3 sway bars front and rear (middle setting). Ride quality is horrible - street and track. Lots of "porpoising" over bumps and pavement seams. Have set the coilovers to full soft, full hard and mid setting - nothing seems to settle it down. Any suggestions as to proper set up to minimize the bouncing? Thanks in advance.