No power after 2000 rpm

I would start by changing your fuel filter and if that doesn't help, have your catalytic converters flow tested.

Check the fuel pump output. Some will work but not have enough output for the instances you describe. Find a place that can test the fuel pump pressure.

Check oxygen sensor

if it is driveable, but seems to cut out, and bog down at sporatic times, and speeds then odds are it's the distributor. (the electical flow is intermittent when it should be constant) if it only happens at higher rpm then it could be the cam position or crank position sensor

Mine has a flat spot around 2000 rpm ... which I've continued to ignore. Others have suggested that the Throttle Position Sensor needs adjustment.
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Most likely its your transmission slipping You will need to have it checked by a mechanic if the rpm is double then it has nothing to do with the turbo, if it's a automatic it means the clutches are slipping or if it's a standard it means the clutch is slipping from being worn out or the pressure plate is wore out.

I assume its the 6.0L diesel...If so sigh......double sigh.. I had one of these...triple sigh. I need a bit more clarification. How many km on the engine/vehicle. Also, you say that it blows black smoke while running at a constant speed at 2600 rpm, or while you are accelerating to 2600 rpm. Also, when you say the boost goes down, does it decrease by itself, or when the throttle is let off. The boost naturally goes down when the throttle is released (not trying to be a ****, i dont know how much you know). However, if the boost is going down by itself, while the engine is under load (its not supposed to, it should stay constant) it could be a couple of things, which "can" contribute to black smoke. If there is a leak anywhere from the turbo to the intake of the engine, it will cause the engine to get less boost, which means less air into the cylinders, which means black smoke. Check all of the connectors/tubing coming from the turbo to the intercooler, and from the intercooler to the intake manifold and see if there are any problems. The more costly problems which results in boost going down, and black smoke, deals with a problem with the wastegate on the turbo (controls how much boost is produced, and when too much is being made, it will bleed off excess pressure). So if your wastegate is malfunctioning, your boost will go down and you will get black smoke cause the engine is not getting enough air. also, around 160km...80mi, the injectors "can" start to go on the 6.0L diesels....I would check the turbo for leaks, the tubing for leaks, and the intercooler for leaks (a big rock can punch a hole in radiators and intercoolers...intercooler will be in front of the radiator). I hope this helps

hallo
remove, clean throtle body with throtle body cleaner or nitro.
Marko

Sounds like the Altinator is going out. At higher RPM it is putting out enough power to keep the car running but when the rpm gets below a certain point there is not enough power coming out of it to keep the car running.

Go to pelicanparts.com go to the 911 tech area for great help.

Jim