I just made a post on this manifold. Single plane and great low end torque. I had one on a Ford build I did years ago and was totally impressed. Never seen them compared on a dyno though...
I ran one for years on a 71 340 it was great for low end but is short and small port so top end was realy lacking.
The same goes for performer intake both have smaller ports like a 318 head good for "street use" on 340-360
