03 cummins lacks power

[bunti]

hey guys im new here.i have a 03 dodge 2500 5.9l cummins truck. i just overhauled the engine i.e. rings pistons bearing valve seals etc.. fitted it back in the truck. when i just started driving it it had no power, but eventually by driving it more n more i saw the power coming back every day. i went on a 3 hr country drive with it n there are times when it feel sluggish and has no power with a lil black smoke. then there are times when it comes back n runs great. ive got no codes related to this prob btw. just one about fan speed n another for brake switch. ive noticed since this week that this doesnt happen at nights when its cooler. now in the day time it sound like air is rushing out from under the truck but ive checked for leaks thoroughly. i even took out the intercooler and checked it (didnt pressure test it tho). i cleaned my iat sensor this morning but i havent tested it again since. i also checked the wastegate and its working fine.can anyone help me to find my problemgonna fill out my sig now

[CUMMINSDIESELPWR]

get the cam and gear timed properly when you rebuilt it?

[bunti]

yea i marked it n fit it back the same way. however i found a leaking intercooler hose. the ring on the hose had tore a hole in it n was also hiding it so i couldnt really see. now am just gonna change them all. ill let you know if this solves it.

[AH64ID]

That could solve it, with the way the ECM monitors boost before fueling it could present itself as low boost and fueling, with a little accompanied black smoke.

[bunti]

i went on a mini vacay in negril (3hr drive), and on the way down it had no power.on the way back however it gave no problem at all the power was back going up hills i was amazed myself at the truck, it was hauling ___but still going up a hill and the temp went up to about 190 it started to lose power again and the fan wont kick in (no thermostat btw). i saw a friend on the hill and stopped for 15mins i had to turn the ac on so the fan would kickin, when i moved off, ____ went crazy. the truck tore up the hill. on another note. whenever it loses power on a hill in 3rd gear the oil pressure seems to be dropping, n it continues till it reaches below 40. then it goes back up when i reach the top. this doesnt happen when it hauling ___. what could be the cause of this? im guessing there is a sensor losing power at times. could there be some ground that i didnt put back in the right place? is the ecu? grounded outside its loom?