Misfire, codes P0300 and P0181

I've been having issues for a while now. Spark plugs, cables, distributor, fuel pump have been change, no leaks, O2 sensors looking good, all cables have been strapped and move out of hot surfaces areas. Have a P0181 as a possible problem, but fuel temperature sensor was replaced along with the new fuel pump. The car misfires a little bit on startup but it gets worse when it reaches is normal engine operating temperature. It feels like is adding more fuel than needed when it gets to the normal operating temperature. Downpipe was crack so I changed, thought it was the problem but is not. Also has new catalytic converter. Haven't touch fuel injectors yet. Any other suggestions please let me know. Thanks.