i had a l20 (the four not the six) that i put the biggest dragrace cam that crow make, Seton (glenn's dad) Motorsport headers ,2.5 inch zorst,twin 40mm webers on a datrally manifold.....bored 60thou and cleaned up the ports(not ported out, just cleaned)
standard dish type pistons, and it pushed my datto 1600 to a low 14.......
it had bugger all comp as i was going to supercharge it....so if u have high comp, injection, ported and pipes...it should go hard i dunno why it isnt....is ur cam timed properly?