What diag did you use? That fault would indicate number four injector may not be working properly. But it could be other things. Check connections to plug and wiring first of all, number four injector signals ECU injection point. Then ECU from info from CPS modulates timing solenoid to adjust injection timing. If that is not functioning properly you will get a lack of power. But if number four injector is totally duff MIL lamp should be on. Fit your bits and see what you get. Look at pipe from under manifold to MAP sensor bolted to top of fuel filter. Make sure it is sound with no cracks or leaks and that where it fits to manifold is clear. You can clean MAP sensor air inlet with a little contact cleaner and a gentle blow with an air line don't poke anything sharp into it. Cleaning out the intercooler maybe a good move also. Paraffin swished about in it several times will do the job. Make sure it is well drained before refitting. The loom plugs should not reach to swap over incorrectly placed sensors you will have to remove them and fit them correctly. Easy to do with manifold removed. First one MUST be Blue second one MUST be Green.
