1994 Chevy Truck engine ticking

1994 Chevy Truck V8 Four Wheel Drive Automatic 141k miles

I have a loud ticking noise coming from my driver side valve cover. I have already replaced my lifters and inspected my push rods and rocker arms. What else can I do to try to fix it. It ticks loud while in gear and stops for a while when its in park, as I push on the accelerator it ticks with the acceleration. It tends to run a little sluggish and high rpm's.