Wasn't it the water injection that caused the massive smoke output?
I've heard that on jets the water added "mass" to the flow which increased thrust. Or was it used to cool?
That sounds pretty reasonable considering that's what you'd want in a jet. I don't know about the smoke so I can't really speculate but it's plausible. The Harrier uses water for hover and you definitely see smoke coming out of the nozzles when it's engaged. I don't know many specifics which is pretty clear to begin with and less so regarding jets the use of WEP or Water Injection in jets.
I read something about that when I was reading up on the water injection systems earlier. The water increases the mass being pushed out the engine which means more thrust. It also doubles its use by cooling to prevent or postpone overheating. Unfortunately the water thrown in with the combustion stifles or quenches it somewhat and some of the fuel doesn't get burned, and that's what explains the black smoke.