What function specifically are you using in andorra? (do you mean additive blending?)
Code:
for i := 0 to 2400 do
begin
   gui[1].DrawAdd(AdDraw,AdRect(0,0,16,16),1,250);
end;
I can do the above with an average of 300 FPS. I think it may be your computer or drivers, unless you consider 300 fps too slow...