Looking back at you other/first? post did you fix anything? You said black smoke and sputtering and a top speed of 45. Who did the rebuild? Going down the list of maybe's, and hopefully somebody will chime in, the timing gears off a tooth. I will add this, I had one of the Jamboree edition CJ's some time ago. I drove it to work once and a while which included a long 7% long grade. That thing came with 2.73 gears and It had 31's and an auto trans. Id have to drop it into 2nd to get up that grade and floor it to keep up at 55ish. But, back to that black smoke. Have you pulled a plug yet to see if their black? Plug reads can help a bunch.