Aaaaahh ....now more critical info come out! There's usually more to the story. LOL.
Well, anytime someone works on an engine, besides the work they did, even if they did a great job, sometimes collateral damage occurs unintentionally and mechanics never know it unless someone lets them know. Connectors can get broken, sensor wires get pinched, Maybe the variable timing isn't working ...headgaskets could leak, pushrods can get bent. Crap in the fuel line to the injectors. Wrong parts got used. Didn't get a good seal on the intake gasket. Coil pack slid off the fender and cracked when it hit the concrete floor (stray spark now). Mechanic wipes off the dust with his shirt, looks around to make sure nobody saw it ....then and installs it
. Spark plug fell on floor and cracked the porclean. It opens up all kinds of possibilities. Or, it's entirely possible what you're experiencing has nothing to do with prior work.
That's why I suggest you start with basic troubleshooting. Because right now it could literally be a bunch of things. And there's only one way to rule out the basics. If you could do a leakdown test that would be even better.
The other thing to do would be to remove the valve covers and turn the engine over, watching the rockers move the amount they're supposed to. Or better yet, put a dial indicator on each rocker, turn engine over by breaker bar. Write down the recorded lift for each rocker. Yeah, maybe the new cam there's a problem?? Or they had the head re-done and the 'new summer kid' at the machine shop goofed something up. You MUST ensure the basics are good and work up from there.
If you discovered the rocker lift was off on one or two rockers, then you know what to do next...