Hi since the lovely spell of hot weather this last week. I go to start the car before and after work and its coughing, spluttering, chugging and farting. Then the revs kick in and it starts to idle correctly. All is well

settles down and off i go.
I have a 16804 cat bank1 code which ive not got round to sorting. Is this whats causing it?
Personally i think the cats had it as im now at 102550 miles. And this fault code is logged in the memory.
I am however getting a decent 37mpg and 42 on a good run which is why im not thinking lamda probe. Unsure?
Any thoughts or suggestions from the knowledgable would be much appriciated cheers.