2004 Celica . Steering rattles and knocking feelinf when car approaches 50-60 kmh....rattling continues as speed increases .but quiets down when speed reaches 90kmh. and beyond.. front tires sent to 2 different tyre shops and balanced... Its something to do with Tie Rods?? cheang

remove valve cover and inspect the head --rockers valves push rods guides etc

I had an issue with the rear sway bar links that caused a knock and rattle, the sway bar keeps tension on so it is hard to feel for play.

Not sure on model but to me sounds like its a dodgey valve lifter when the seals start to go they cannot hold the oil and when there under pressure they basically empty them selves hence when you turn the engine off and restart you get a rattle sound untill the valve fills again as long as the cars running ok leave it untill you have to replace them unless there easy to do sone are sone are a pain

Might be motor mounts or struts.

Does the car make this sound when the car has just been turned off and engine is still hot? Lightly push the car back and forth while it's in park. Does it still make that sound?

your front drivshafts have cv joints, these have grease in them which quiets them. once the grease dries up they rattle. even more so when turning . you should replace both front cv joints. get rebuilt units to save$$$$

If you feel this rattle while driving at low speed or turning at low speed it is likely a worn out steering shaft coupler, it is very common.

check for a loose catalytic converter heat shield on the exhaust system first

If it's doesn't sound like it's your engine which i am thinking not. Check to see if there any heat shield that may have come lose, like the heat shield to the spark plug wire or heat sheild along the down pipe. 
Good luck and hope this was the rattling your taking about as it heats up it expands and tighten's up.

have they checked front c.v. joints, as far as knocking noise it could be several things.