I recently had my 2004 Jaguar X type tuned up-fuses changed, coils replaced etc. Now, it's not running nowhere near the way it was running before the maintenance was done. In other words, it's running worse. It begins to sputter when i reach around 60mph... What could be the cause?

 

The most obvious answer is something is amiss from the work done. Now the problem is isolating it.The following is a list of possibilities and I am sure there are more I haven't thought of.
1. Wrong plugs or incorrect plug gap.
2. One or more defective replacement coils.
3. Lose or damage coil connector plug.
4. Lose or broken coil wires.
5. Intake manifold gasket leaks.
6. Vacuum hose from rear cam cover leaking.
7. Vacuum hose from intake manifold leaking.
8. .PCV hose from cam cover to manifold leaking
9. Throttle body to intake manifold leaking.
10. Electrical connector left unconnected.

At any rate an error has occurred and it will have to be found. The car is stuttering around 60 because the ECM is in restricted performance (limp) mode.

 

Is this check engine light on or flashing? If so, have the codes read and that will point on on where to start. If not, my first guesss would be the plug gap.