414 Dyno results: Missed combo?

I have a friend/customer who put one of these on his 440, watched Him make a few passes, laid down a cloud of gray/black..........never-ever did that before, have any A/F
#'s from the dyno before & after? I was thinking the increase in vertical airflow velocity might add too much pressure to the bleeds, but apparently not, curious................

I have read that the X-treme lid interferes with the incoming air from the sides and causes turbulence even though it flows more. My experience seems to support that idea. I tried one at the strip 10 years ago and when I took it off I picked up 2 tenths on a mid 12 car. J.Rob