Agreed, from what I've read the stock set up is very lean, and when you do the upgrades it makes the problem worse. Better airflow without added fuel. Without it you can experience a bit of hesitation off idle. I know when I did mine, before changing the jet and tube, it would have to think about it before accelerating from idle.
Now I have my idle set very low, I like the RUMP RUMP RUMP sound rather then the standard lawn mower noise. But she'll roar when you crack the throttle, no hesitation at all.