As Mark stated, different carb and motor combos change the signal strength and therefore will pull fuel sooner or later depending on the additional holes/bleeds in play. I know a 1050 Dommy on my car is way more sensitive to idle and hi bleeds compared to the 1150's I've tested which are more stable across the board w/similar bleeds and settings and the t-slot really helps a bunch in low rpm steady cruise before booster start up. BLP says they use a certain size in just about everything both 4150's and Dommys but my testing proves bigger as in the .070's I tested recently giving me 9.9-10.5 afr's compared to the .055's that produced steady 12.8-13.5's. I now am trying .059's and it's 11.2-12.0 so this alone on a street driven car has a Hugh influence. The pressure differential between emulsion holes and the bleed pack and the amount and sizes of given bleeds affects booster start up and yes, the boosters will be active w/out being under load. I'm still learning a bunch of stuff and sometimes a change that SHOULD do this or that, does not then the fun begins............I did a Dommy for someone on here w/.600 id boosters for a Hemi and it just could not pull enuff fuel no matter what bleeds or jets were used on the dyno and street. He sent it back for .0500 id boosters and an external linkage kit and boom, lots of controllable fuel now..........fun stuff.............