Faulty fuel injector(s) can cause 1. Hard Starting 2. Poor fuel Economy 3. Rough Idle 4.Loss of power during acceleration. Believe it or not, I have changed mine in a Bonneville at 90,000 miles as a regular Maintenance part. Injectors wear out just like any other part,reason being the internal parts of the injector such as springs,plunger,needle seats start to weaken and will not let the injector open and close thus sending too much or too little fuel. Remember if you change injectors, change the O rings and seals as well. About the plugs and wires, Were the plugs gapped to correct specs(if needed). Check the wires to make sure they are not crossed or they are connected securely. A new fuel filter would likely help also.