Someplace we've delved into some of the better explanations of why mid and high IFRs are sometimes used. One of those situations that might be relevant for us is to give a shot of fuel during throttle opening. I would think that could be dealt with in pump shot, except of course on vacuum secondaries. That said, I moved the secondary IFRs on my 3310ish vac secondary carb but need more track time to see what's going on.