heres the deal, coolant going trough an engine to the point the oil is milky no good. I'm not gonna speculate but engine bearing damage can occur but then again i've seen ghetto camrys that have driven for 10 years with a leaking head gasket. The engine code is very important to see, why you didn't have a dealership look at DTC I don't know why, or you are in a auto program, i bet you have more then 1 obd II scan tools. Albet it was primary 02 sensor or cat efficentcy related, why didn't you just take it to the dealer and have them probley end up replacing the primary 02s and cats, they don't care or know that you fuked the pooch on your crappy engine mod, they just wanna fix it and get it out the door.