basically it sounds like your low speed needle is really rich. really rich or really lean fuel setting can cause glow plugs to go bad, as can flooding the motor.

and a rich low speed needle will casue it to "bog" or be slow accelerating.

the low speed needle is on the side of the carb. to lean, screw needle in a bit. dont go crazy, adjust 1/8-1/4 turn at most. and remember where it was before you started adjusting it, incase the adjustment doesnt improve performance you can go back to the previous setting.