05 Tacoma Code

Hi Folks, new here and in need of some help. I have an 05 Tacoma with V6 engine. Been chasing code P0306 #6 misfire. Replaced plugs and #6 coil pack but still getting code. Runs rough when starting cold then smooths out. Where do you suggest I go next?
Next question. Have a knocking noise when idling in gear. Can put my hand on air filter housing and goes away. Could the air box seal need replacing or would the latches be getting weak?

 

Have you been loosing coolant? I hope not. I think that the #6 cylinder has been known to have head gasket leaks.... I would get this checked before it gets worse.

I could be wrong, but you have replaced the coil pack and plug...

 

Yup usually it's a blown head gasket with this problem

 

Unfortunately you guys nailed it. Just checked and coolant was low. Time to dig out the emergency cc.

 

How many miles does your truck have?