M2Dude
I can think of no other design in the world, before or since, civil or military, where a supersonic engine/intake marriage gave such incredidable levels of performance, stability and predictability.
Well, the XB-70 had an inlet with an efficiency in the 90% range but it wasn't as stable/predictable (it suffered unstarts).
911slf
I believe that engine #4 was limited to somewhat less than max power until 60kt because of a vibration issue.
What kind of vibration issue occurred?