Changed plugs now car runs worse than ever

Which engine do you have? Is it equipped with coil-on-plug or spark plug wires? Either way, I suspect after removing coils / wires, you will create spark leakage due to dry rotted boots that cover the spark plugs. You may require coil boots (if coil-on-plug) or ignition wires. Hands on testing, for sure, is needed. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops