2004 chevy trailblazer_ls_ext
When I replaced the plugs in both of our 4.2 I6 TB's, the first thing I did was to give the plug just a tiny tweak tightening it. Then loosen the plug until resistance was felt. Tighten it up a turn or so, then loosen until resistance is felt. Repeat the process until the plug is out. You do not want to gall the threads, and this process will help prevent that. Remove the plugs only on a cold engine. I always use a small amount of nickel anti-seize on the threads of the new plugs. Torque to spec. 13 ft. lbs. IIRC, don't have the book handy.