grounds are the connection to the body which flows back to the battery negative. For DC (Direct Current) electric items to work you need 2 things. Positive going in and ground coming back. Take away either and it doesn't work. Loose/corroded grounds inside the bulbs and at the body connections...
2003 TJ D35 rear and D30 front low pinion. If I were you and it's being lifted, I would get an XJ front diff to swap in (high pinion is better driveshaft angle for lifting) Maybe find someone with a 4.0L TJ that wants those nice gears and swap diffs with some $ in your pocket you can put towards...
For me, when I click on the email showing new posts, I get sent to the first post on the thread every time. I usually click the for sale one and then choose new posts link at the top left to check what I've missed and get the newest posts that way.
Clogged injectors? Can of BG's 44K or Amsoil PI should help. When my ignition module was corroded it atced like that too. I also had to clean/set my TPS.