4A-FE Timing on mark but knocking

[WildsideCreations]

So im the guy with the 91 Celica ST 4A-FE with 300k mils on it. Engine was rebuilt by a reputable shop at 250k. (not my choice btw. Got the car after the rebuild. I would have done a swap.)
Anyways I have been playing with plug/timing combinations and cant seem to iron out the knocking. ***ANY*** sugestions are going to be welcomed at this point.
Heres the deal right now: New Bosch Platinums, New Wires, New Cap, New Rotor, New Oil, and Good battery. NOT making smoke at all. Passes Smog no problem. plugs dont get fouled. and not burning oil.

When under almost full and full throttle the engine makes the pinging sound that i have th understanding is knock caused by?.... detonation? anyways, the engine runs fine otherwise and if you have the radio up real load and windows up and the AC on full and you ignore the sound completly, the car seems to run like brand new. However i KNOW this isnt good for the engine or my power/economy.

PLEASE HELP ME!! At least give me some thing to try. I am out of ideas.

I need to edit this and say the knock happens under load on the engine only. not while idling or even normal driving. Only when i floor it, wich is alot since this puppy has 90HP tops. (laugh).