Truck Repair: N 14 select plus on 2002 volvo, gasket thickness, cam follower

Question
After mechanic changed 2 cam follower gaskets truck has not been the same. When I press throttle truck acts like its chocking as if it is gettting to much fuel. I have to sort of balance throttle pressure constantly to find a smooth flow when driving.  It idles very ruff. If I have a heavy load it feels like truck has no power at take offs. It takes real long time for it to pick up speed and same time feels like its choking. Mechanic connected computer it gave him inj.4 @ 14-16 rpm failure so I changed that injector. Still same problem. When I rann the truck diagnostics self test it gave me for engine fault MID 128.
For the non-spec. system it gave me fault code MID 127 not responding.
Thank you
Dino

Answer
If it all started after the cam follower gaskets were changed first thing i would check is that when he changed the gaskets did he change them with the same thickness gasket. The followers call for a specific gasket thickness which if not correct will advance or retard your timing based on the thickness of the gasket by just a bit. If trhats all correct how far did he tear things down. could be the overhead not run correct alot of times the overhead is not run correct on those intake valves are always inside rockers. If he pulled accesory drive off that has to be placed in time. if he didn't run the whole rack after replacing the injector it needs the overhead run on at least that cylinder.