With turbos there could be any number of things that will cause a knocking or pinging and a loss of power. First know any time you here a pinging you should get off the gas! You can cause a lot of damage by letting it ping or detonate. Picture the piston coming up in the cylinder and before it gets all the way up a sledge hammer smashes it back down, but it must finish comming up cause the crankshaft is still pushing it. This is what is happening when it is pinging. It can blow head gaskets, break ring lands on the pistons or worse.
Now that this has been said you can better understand why you should never here it detonate. Low octane fuel, lack of fuel supply, too much timing, no after cooler, overheating and too much boost all can cause this problem. This will also cause your engine to fight it's self to run and cause a loss of power.
I would start by using the best fuel you can buy and never stray from that. Start with about 5 PSI of boost until you can get it to work properly. Set your timing to factory specs and never less then 0* or more than 12*. Make sure you have good fuel delivery (fuel filter clear, good fuel pump, clean injectors, ect.) I would never run more than 7 PSI without a intercooler, the air temp will be so high it will cause it to pre-ignite. Also under higher boost it is harder for a spark to jump in the cylinder so the plug wires start to leak (ground out) under boost. This will show up like the engine shuts off under boost, but runs fine otherwise.
I may not have the answers you are looking for, but I have had lots of experience with turbos and high boost. I will leave the Toyota specific help to the people that know Toyota, This is just general advise.
Good luck,
Mark
