Lack of power in volvo penta AQAD41A

"we have this type of engine i

"we have this type of engine in 22 feet fishing boot. the power during the year has been very good . now te engine is just getting up to 1.500 revs and from then it takes long to get up to 2000 revs with a lot of smoke. we have rebuild the injection pump, all injectors are new, exhaust turbine is rebuild, rebuild cylender head. we have come to the conclution that there is lack of air, next step will be to messure pressur in the inlet manifold. the water coled elbow from the exhaust turbine is rebuild and not original, do you have any experince that this elbow is giving problem. with regards and wish for help. Heiðar"

"Heidar, I'm a novice. How

"Heidar, I'm a novice. However, my experience is that the air supply to the turbocompressor is critical for power. My AD41 is not used during winter. When first used in the Spring one engine must be helped by the other to gain more than 1650RPMs. When power is very, very slowly applied during first use, the turbocharger functions and eventually the engine operates normally. Afterward there is no problem at all. I would be certain that your air filter is new or very clean without obstructions. Good luck.
pv"