Ok so what you are saying is this ...
The xbox motherboard was fragging unchipped ( stock ) and then you fitted a duox2 chips and it frags also.
So the problem is not LPC related and something is wrong with the motherboard and it doesn't work at all.
Normally if people are having trouble with a chip install i tell them to get the motherboard working first ( stock ) and then try adding the chip.
In this case i guess you should remove the chip and look / test for any faults depending on your skills you may need to take it to a pro as there is so many things that could be wrong with the motherboard it's not funny.
Burn't trace , Blown cap , etc etc etc
HackDaBox !