I have a 2006 Xterra with 132,000 miles. When I let off the gas the oil gauge dropped so we replaced the oil pump. It's a bit better but still not right. Then we were told we probably need a to replace the lifters or just use heavier oil. We've tried the heavier oil but sometimes the oil gauge drops and you can feel an odd vibration and/or a rattle feeling from the motor. When you rev it up it's fine. Any suggestions or is it time to replace the motor?