My car was like that too for a long time - lot better acceleration when throttle was fed in rather than just planted. I came across a few other people with the same thing too.
Unfortunately I can't offer a sensible solution as mine only sorted itself out when I fitted the EFXR6 head and cam - and even now it's probably marginally better if the throttle is fed in, but it's not quite as big a difference to flooring as it used to be.
IT'LL GO OR IT'LL BLOW!!!