Test different valves. Cut down an aftermarket 1.940" intake valve with a 9 degree back and then add a minor undercut. Keep the margin reasonable. No sharp edges like an OEM LS3 valve.I did it's called a gt40p. I wouldnt learn anything if I just slapped them on. In a different life, i use to develop and dyno single cylinder engines.
I found something and flow improved everywhere .
400 lift is little noisy so it may flow more at 400 once sorted.
500 ligtvit stalls now . But with no valve in 247cfm. Seems the biggest restriction is the air trying to get around the valve.
Time to take some material out