Unplug the sensor from the wiring harness, and get a special O2 sensor socket from the auto parts store (some loan them out for free) and remove the old sensor from the exhaust bung. If the sensor won't budge, try more penetrating oil or attempt the removal with the engine warm (be careful not to burn yourself).
However, a mattress that is too soft is just as bad for low back pain as a mattress that is too firm. In a 2005 study, The Journal of the Canadian Chiropractic Association pointed out that in a survey, 76% of orthopedic surgeons recommended firm mattresses.
Gel Mattress Types. The different brands incorporate gel in various ways. Some include a gel-pad layer on top or beneath the padding layers. Others pour it into the foam as it sets, or incorporate beads of gel into the foam. Gel memory foam mattresses are the most popular combinations, though gel mattresses are also springing up in latex and and innerspring styles, and even mattress pads.