The pedal box does HELP, but you can still get that lag if "driven improperly" to cause it. It is more like having it in sport mode all the time.. it decreases that dead spot, and makes the pedal more sensitive, but it does not completely eliminate it! It is certainly worth it in my opinion, I do like the pedal feel more like a drive by wire, ie you hit the pedal and the rpm's go up right away.. vs stock and most electronic throttles, there is a slow tip in and a small dead spot.
The SS mid pipe wasn't actually that expensive when 21M235IXGC pieced it together... something like under $300? I also "think" that the X1 downpipe itself might fit, but then again you need to deal with the front O2 sensor and a check engine light. For me I need a yearly inspection that monitors all of it, and the gains is not worth the headache for me at this point in my life
The limp mode is mainly the car either boost spiking too much or the timing might suffer.. high heat doesn't make the car happy. Again, I'm pretty lucky and I haven't had it failsafe yet in map2 no matter the season (once the boost limit was raised as you need to do in the jb4 custom settings). 21M235IXGC saw the overall boost increase with just the midpipe, which would increase your chances of hitting that limit and putting it into limp mode.