Help is needed desperately

I would have plugged a computer up to it before I did anything.
Lot cheaper in the long run...

 

@AModelCat

 

Air filter.

 

Looks like you've done all the right things although I would of started with the simple stuff first things like the air filter, fuel filter the cheaper options first see if that changes things, it really makes a difference if your engine can't breathe same deal with fuel filters, next on the list would be the turbo, we used to have these issues here in OZ with the adblue which is used to stop pollutions levels, if the adblue cloggs up this greatly reduces the horsepower under load but will work fine bobtail. Not sure if you use the same system in the US but if your adblue is not working this will also effect the powertrain. This is what I think may be your issue if your losing power under load but not when its bobtail.

 

First, what engine does it have? MB? Second, I would have checked the settings in the ECM/Computer, how castrated is it? All the new parts in the world are not gonna help if it’s programmed for 210 hp.

 

Why didn't you get a dyno done to see how much power it is really making?

 

You are throwing parts at the truck hoping to fix it. You must have money to burn. Your comment about how well the truck runs bobtail means that you have absolutely no idea about anything. An unscrupulous repair shop could easily clean you out.

I am not being helpful, am I? There’s really no point in me trying after you’ve ignored the ECM/dyno tune recommendations. If it were an injector, charge cooler, fuel air filter issue, the truck would still run like garbage bobtail. Someone may have programmed a beancounter tune into the ECM. With a bad tune, the truck will run like arse regardless of the parts thrown at it.