After I fitted my Stealth FX I went out and tried it in all different settings doing hard shifts from 2nd to 3rd - I tried PB, atmo, 50/50, soft spring, hard spring and 50/50. Mine is fitted down by the throttle body as I have Nizpro stage 2 plus. I can confidently say that the least amount of lag, for me, is 100% atmo and hardest spring setting. Taking boost away at the butterfly clearly has an impact on throttle lag, for me anyway. Somewhere on this forum there is an excellent article by Simon Gishus that explains why. Hope this helps. Velluto