Q: Car sputters and has weak power after new spark plugs and ignition coil were recently replaced

There are actually several possible causes for the engine to sputter. It is possible for there to be a vacuum leak, a faulty oxygen sensor, a catalytic converter that is starting to show signs of failure, or even a possible problem in the fuel system. It will be necessary to do some further diagnostics to determine which system is causing the problem, and then figure out which part in that system is the root cause. For example, if it is found that there is low fuel pressure in the system, it will then be necessary to figure out if there is a weak fuel pump, clogged fuel filter, or something going on with an injector. If the problem appears to be with the ignition, there could be a problem with a spark plug, ignition coil, ignition control module, or a fault in the wiring. I understand you said that the plugs and coil had been replaced, but it is possible that one of them have failed again, since the problem is recurring. If this is something you could use a hand in identifying, I would suggest consulting a certified mechanic, like those available at YourMechanic.com.