Shaky on startup

[ijag]

For the past 1-2 months when starting from a cold start it has been having a vibration for 10-30 seconds and then it smooths out, shortly after this started it has been shaking when pressing the gas but happens at a higher speed 40+ but then it smooths out when letting off the gas
99 Explorer 4.0 ohv

 

[ijag]

Changed spark plugs,wires, and coil a few months back. New fuel pump and filter. Cleaned maf. Changed pcv valve

 

[ijag]

Ran the codes
P0303 and p0455
I just found the leak right behind the downstream 02 sensor where the muffler connects to the pipe But could this cause a misfire?