Hi, different Dave W. here. As Dave said, Stock Category autocrossers do some seemingly stupid things, because for suspension we can only change tires, shocks, and one sway bar. So we often make shocks work as springs. Or run so much rebound that the shocks jack down into the bumpstops so those increase the wheel rate. And unlike track events, autocross is all about transitions, some steady-state cornering, and almost no straights. So job #1 is often to remove as much "floppiness" as possible in the chassis with the few tools available.
On running "full stiff" on Koni yellows - I always turn the knob until it stops at full stiff then back off 1/8 to 1/4 turn. Back in the day we were cranking them full stiff on a Neon ACR and the adjuster shaft seized on more than one; when we sent them to Koni they recommended not to drive while dialed to full max. Note that Koni yellows only adjust rebound, with some crosstalk to compression in the top 3/4 to 1/2 turn.
If NNJR was running Meadowlands/Metlife parking lot, the surface is pretty smooth with long undulations if you're crossing the drainage swales. (Pay attention if you can use them as "banking" when walking the course.) I'd agree with (near) full stiff on the shocks as a start. Unless it rains, in which case the sealer can get treacherous, and you want to run closer to full soft.
As far as tire pressures, yes, they do matter, but if you're just starting autocrossing, being +/- 3-4 psi of optimal is good enough; just don't roll the sidewall or run crazy high. It's much more important to learn to drive with "aggressive smoothness" and find the right line on course. The biggest improvement in your first few years of autocrossing will come from more seat time.
I should have been clearer, when I said full stiff on the Koni, I meant a little off actual full rotation as the other Dave_W specified. I think they call this out in their instructions.
Sorry for not being clearer, but thanks for the correction.