2003 Honda Accord Car shakes at idle and then shut off

That was my thinking the case was very remote. I was 100% sure that I did not pump any diesel into my car which they are claiming. I had asked him three times if they had check the IAC and air intake. And they told me that the computer did not come up with anything. I also told him that if the system is weak the computer my not pick it up. This was based on this web site. Which is very helpful. After few hours and not making him change I had him go ahead and remove the fuel. After, that was complete they came back and told me that there is another issue. Which I think was the real issue in the first place. They came and told me that the check engine light was coming on. Which of course I have never seen. They told me that the following code PO301 and PO303 which is multiple misfire codes where malfunction and had to be replace. Can you please let me know if this second find was the really cause or the second item.

Thanks.