Error Code 51 and 52...
 

51: "Switch Signal"

I know I did not make the mistake of having the AC on or hitting the gas while checking the engine lights. So, could this be from a bad ISC unit? I know I have a small coolanty leak somwhere in that area. I believe where one of the hoses connects to the ISC.

52: "Knock Sensor"

Uh oh... :-)

Could this be from using premium gas ?

BUMP

Any ideas?

Replace knock sensors will most likely clean the problem up.

With them playing up the computer will think there is pinging and will put the car into 'limp' mode, will drive like pooze.

Toyota wanted something like $398.00 +gst ea when i had to replace mine, paid $6 ea second hand, i suggest you go second hand ;)

Yeah. I agree on him on this issue, Just try to replace the knock sensors. I used to have this problem once last February.