poor acceleration

hi . my 1978 fj40 have a good acceleration in low and medium rpm but poor acceleration in high rpm and engine don't work smoothly in high rpm (may be some cylinder not work in high rpm) and engin and car vibrate in high rpm . in 4th gear engine haven't a good power . but in 1st and 2nd...

Last weekend, I went to the sand dunes with the local off-roading club here. Unfortunately, I couldn't even make it up the first dune. The leader of the group drove my tuck to see what was wrong with it, and he said it should have much more power, and that my RPMs don't go above ~2300 even when...