All right, I still seem to be having some minor problems. After everything else mentioned above that I have done, here is what followed:

1- My initial impressions of driving with the timing at 2.5* BTDC were not as good as I originally stated. It seemed to help some, but not that much.

2- I filled up with 89 octane fuel several days ago. The spark knock is almost completely gone, but then again, the timing is still set at 2.5* BTDC. I still get some spark knock when the engine is under a load when I am accelerating.

If I set the timing to stock spec of 5* BTDC, it's gonna be worse. Seems to me that there is still something not totally right. So that's where I am right now. Any other advice?