My manual 540 knocks whether in or out of gear everytime when i am in the range from about 55-60mph. driving me nuts. any one else experienced this? she has about 84K on her and is otherwise in prime condition.

engine is knocking? or just a knocking? Nikasil engine?

A search would have revealed many threads describing failing thrust arm (aka upper control arm) bushings causing a front end shake at 50-60mph.

Just wondering, do you ever get oil warnings? Low level, low pressure, etc...?

5 Spd. or 6 Spd?

check ur plugs and wires.