ST205 Mechanical help needed! Car stalls Options

[TEAMFaint]

I am by no means mechanically inclined at all however I would like to try and diagnosis this with some of
your guys` help instead of having to take it into my Toyota dealer.
Here's my situation:

When the car first fires up, it idles nicely at 1000 rpm, smooth rpms all over, drops nicely back down to 1000 rpm with ease.
Now the cars engine is warmed up, and now the trouble hits.
Car still revs up fine but starts to dive down to the 800 mark and getting rough, in some cases when I am hitting the brakes abruptly or I press the clutch in for a neutral coast, the car will actually stall out and drop from whatever RPM I am going, (typically 3000) straight down to zero with no hesitation.

I am at a loss as to where to start, ideas my friends? Need some helpful insight from some experienced members with the 3SGTE world.

-Kellen.