timing the same for headers set up? lack power?

back pressure makes power below the engines power band or picks up the torque under the cam.

who races below the engines power band?

street cars.


with low back pressure you'll have to richen it up.

the scavenging of the header is pulling the bah-gee-zuz out of that 1 barrel, jet up.
if you have any cam bigger than 252*, even the factory 2 barrel won't due with lil jets available.

I recommend a holley 350 cfm 2 barrel, or up the jet size and live with it.

jmo