This is a black art, not a science, unfortunately. The best we can do with theory is stop you from blundering around completely in the dark... it's still trial and error but at least you will know what to try...

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8