The description is not the best, though the lack of go is not from the torque converter.
I think the trouble is the pump gasket, that is dropping the line pressure at idle. Beav is on the money, maybe not sucking air as much as dropping pressure.
When the engine is idling the line pressure is lowered, When you hit the go pedal the A solenoid increases the pressure and away you go.
The trouble with the low line pressure, is that the 'low and reverse clutch' is not applied quickly enough, to prevent the gear train from rotating backwards, so nothing happens till the clutch applies and away you go.
The effect of no engine braking, in selected 1st gear, also shows up the low and reverse clutch, as the throttle is closed, the line pressure is reduced as normal. The lower pressure is not locking up the clutch so no engine braking happens.
The box has to come out, the pump gasket could be fixed without doing the rest. Though you must expect that at least this clutch will have appreciable wear so it would not be a long term fix.
All the best mate.
Harvey.
