Need some help with confusing timing issue

[scsindust]

On my 89 in my sig, I hae tried to set the timing, but can't get it right. I know the PO put a reman'd motor in it. I found TDC on cyl #1, and adj the dist cap to line up with the rotor on cyl #1 wire. It seems it only runs good at like 20* BTDC. and when the EST is hooked up, it goes way back farther! So, do I try to get it so it is fixed and is set to the right timing, or just turn the dist cap till it smooths out? Which brings me to my next question: Whe I turn the dist cap, it runs best at the point when it idles the highest. does this sound right? It seems at its best that it still doesn't run 100%.