ive tried my best to accurately est. the fly hp of my 302 using Dyno2000 ver. 3.06 program. and with it set up as stock exhaust manifolds w/ mufflers it was showing me making 268hp at 5500 rpm then changing it to small tube header w/ mufflers it was showing me making 315hp at 5500rpm. does that sound crazy or does it make that much of a difference 47hp? i am planning on installing tri-y headers so i figure they would be small tube.