Misfires on cold start

Problem started a few months back. Car misfires when I start cold. Stops misfiring when warmed up completely. I have changed catalytic converter, fuel pump, fuel filter, ignition module, all spark plugs and all injectors. Check engine light on throwing code cylinder two misfire. But in the beginning threw code cylinder one misfire. I replaced the injector and spark plug for cylinder one. Ran good for two months, now says cylinder two misfire. The mechanics I have taken it to cannot figure it out so I am looking for online help.