cam help.

I'v been messing around with my dyno 2000 program, with cam specs and it seems anything over .400 lift actully hurts a 200. I have all the specs for the engine put in, the turbo, flow chart, ect... and a cam with a higher lift than .400 messes with the upper end beyond 6,500 which I'm not worried about, but it also slightly lessens the curve from 4,500 to 6k, equals to a couple hp. but I'm just messing with the simulator, and valve overlaps are 20-30, yesterday I had 1 with a valve overlap of -10 and it was like the best 1, but I cannot remember how I got it. what would give a very low overlap?