Modest gains on milder engines yes. With a large cam high flow head and/or stroker then headers can gain 50 hp or so over manifolds. So how much hp headers gain depends on engine combo.
If you go with TTI exhaust with manifolds then decide later want headers you can pull head pipes out of H pipe and swap in shorty pipes to hook to headers. Thats what I did I used to run 340 manifolds then when orig eng got replaced with stroker eng switched to headers.
View attachment 1716213880
