Well, I sure feel dumb. I placed a large brick on the accelerator pedal, and the linkage was only opening about 1/2 way!
It looks like it was out of adjustment to begin with, and somehow got bent during the valve adjustment.
It's now adjusted perfectly, and oh man...this is the most power the car has ever had!
Rechecked the valves and they are all perfect still. However, there was something I saw inside the valve cover that has me a bit worried...Inside the timing chain's cutout in the valve cover, it looks like there is a large scratch mark in the metal, like the timing chain has been rubbing it.
I didn't have time to check the chain stretch, but I will ASAP!