Biggie,
You should first verify that your accelerator pump cam acrew isn't stripped. I have seen this happen more than once. Next, be sure you can insert a .015"-.020" feeler gauge between the pump arm and lever at WOT to ensure the adjustment is correct. Next, check your manifold vacuum at idle in gear. Your power valve should be 1/2 of that value.
If your problem persists, you can increase the squirter size, but in general, a .028" is just about right for most street motors.
Hope this helps...Robert