Switched food too quickly, need advice

First of all, I know I was an idiot to switch my cat "cold turkey" to a new food. I would appreciate advice, not a lecture; I already know I should have done this differently. We started the new food (Innova Evo) on October 6th. On October 14th, he had diarrhea (I only saw the aftermath, and it looked like it came on suddenly). On October 17th he had a small amount of vomit.

Is there anything I can do to try and help relieve his discomfort? Should I get some of his old food and try to start the transition almost two weeks late or should I stick with the new food and wait out the tummy issues?

Thank you.

Go back and use the old food and MIX the two

I was wondering, if it had to do with the food, would there be such a long delay before the diarrhea? And ulti, were you feeding wet or dry?

Forget the old food at this point... just get some pro-biotics and digestive enzymes into him to help him best process the food.

AHHH I cant read thought it was a few days ...

Probiotics and LOW dose Enzymes may help ... BUT if that doesnt your cat likely is the 50% that CANNOT handle evo for what ever reason and you may need to look at simplier foods