hi mate,
my first car was a bluebird sss, and it did something very similar to what u described once. this is probably a useless post as i never figured out what it was.
I was driving along nomrally,then the car seemed to lose all power, it revedd when it was in neutral, but once it was in gear i could floor it and the rpms would refuse to rise, i was just chug chug chugging along. Car would jsut do this randomly once in a while. Happended a few times, the last time it happned i tried to take it to the mechanic to show him, but it just went normal as soon as i got there (that always happens when u want to show somebody something).
Anywyas, i figured it was something blocking the fuel lines, and it just took a few attempts to completely dislodge it. Useless post, but atleast u dont feel alone now