if you're running stock 330cc injectors, then yes you will need injectors... i had some HKS 272 cams and did loose some bottom end, but with adjustable cam gears, as Ij said, and some dyno time was able to boost my midrange power, on a similar setup to yours, by about 40-50 hp...
the engine pulled thru redline and past
but it has been a while... i think we topped out around 379 rwhp... but i would of liked more control over the timing and fuel curves than using a simple fuel piggyback as i did back then...