I feel sorry for you for the problems you're experiencing, but I am not standing with you. A car that is regulary maintained does not mean that car hasn't been abused. Careless acts such as extended over-reving engine or improperly sealed oil drain plug after an oil change can seriously harm an engine without showing any evidence on maintenace records. You have no idea what that engine has been through. Fortunately, you are very lucky that the previous owner of an 11 years old car is helping you out. I would be beyond ecstatic if Lexus entertains an offer to pay to look at your 11 years old engine as there would be countless others waiting in line.