Good fair and honest review.
About the coolant stud issue. That is the fourth of over 200 actual units to date that had this issue. I put 5ft/lb on every unit that goes out the door and all seems fine. The nut needs about 2ft/lb tops. If you put 10+ft/lbs on it you can likely kiss it goodbye. Hope the welding you did in the field was ok on some of the internals, but sounds like all went AOK.
Some tuning advancements may help with the lag impression. Although many customers say they spool faster than stock, I think that has a lot to do with the fact that you can actually hear these things breathing and they still make very good power numbers down low. The fact is that the turbine and shaft are MUCH larger, so it is only expected that there will be slightly more lag.