98 Nissan Altima problems

I own a 98 Altima. It has been a pretty good car but is getting up there in miles, 143,000 but still doens't burn a drop of oil between 4-5K mile oil changes. I keep it tuned up with new plugs and plug wires, fuel filter and air filter. Recently we were having problems with the car shuddering when you take off and make a right hand turn. Finally someone realized it was the motor mounts. I replace 3 to the tune of about $675.00. the car runs a lot better but now my wife says she can still feel it viberate when she makes the right hand turn. We have had the tires rotated, balanced, front end checked for alignment and struts and even a transmission dealer checked it out to see if maybe it was a converter in the transmission not working correctly. None of the above has conquered the problem. Anyone ever had this happen or could it just be one of those mysterious things that only happens when "she" drives it and never when "I" drive it?