Full exhausts to open headers gain

I saw almost 50hp when we dropped the pipes on my Chevelle from the past..... But it was expected since it had Shorty headers and 2 1/2" exhaust to the bumpers which was not ideal for a 540. That was not so much as touching anything else but my friend who ran the Dyno knew it would be the biggest gain he would ever see from just that.....

JW