After driving (engine revvs OK, pulls up OK etc.), running the car 'idle' is a disaster . . . It starts idling at 1000 RPM, then drops to 900, 800, 700, . . . almost zero :-< Adjusting the choke, the engine runs fine again at about 1000 RPM, release it and the engine dies again :-< What could it be ?

What engine is this?????? I assume carb for you say "choke" If every rpm area but idle is fine

did you say 2TB? do you mean 2TC? what year? EGR valve is there to recycle a small portion of exhaust gas into the intake charge. Doing this reduces cumbustion temerature giving a lower emission level of NOX (oxides of nitrogen) very very bad stuff! and reduces engine ping (knock)when you run roach piss for fuel! If this is a carb problem, toyota uses a AAP diaphram on the carb. If this diaphram ruptures it will dump raw fuel into the intake where it pulls vacumm to operate. killing one of the cylinders at idle.