Toyota Repair: Supra Mk3, toyota supra mk3, rod bearings

Question
Hello, i´m from Sweden so excuse my english :)
I really need some professional help.
There is a knocking sound from the topp of the engine.
It occurs around 2000rpm and disappears around 3000rpm.
I´ve tried a loot of things, but nothing seams to help.
The only thing that makes the knocking go away is if i adjust the ignition to 0 degrees Btdc (or later) It should be at 10 degrees to make the car work properly. I´ve disassembled the topp and checked the valve chims, lifter springs and camshafts.
I´ve also: measured the resistens on the ignition coils, igniter and cam position sensor. All is OK.
Changed The spark pluggs and oil.
I tried to have thicker oil in the engine if it could be the rod bearings that was broken. But the sound did´nt change with the thick oil.
Also rod bearings is not logic because i have had the sound for a couple of mouths so if it was bearings the engine should broken down long ago.
I also have tried to disconnect the knock sensors and reseted the cpu, but it is not helping.

I have disgusted this on a Swedish supra forum butt no one can help me.

The Car is a Toyota Supra Mk3 89 With a 7mgte engine.
I would REALLY appreciate help, enough to make a donation if you help me understand what is broken.

Thanks Very much in advance!
Regards: Daniel.

Answer
Hello,I think the next thing I would check is the timing belt, it may be worn which can cause the timing tom be off at that rpm, you can make the knocking go away by retarding the timing so it has something to do with spark advance, it's not a mechanical problem, also check to make sure the engine is not overheating.