it was shown on a dyno to lose HP, haha, at least until turbocharged.
Stock manifold: 141 hp / 144 tq
HO manifold: 134 hp / 134 tq
http://www.j-body.org/forums/read.ph...2&t=400177&p=1
Of course the results are widely disputed by those who have the manifold.
Also, this thread is almost 3 years old.