Post header install and having hesitation in idle

[el_Don]

Hi all, I recently installed a shorty header on my 02 ES. I had to replace the first O2 sensor with a universal one because I could not remove it from the stock manifold without damaging it. I first threw a CEL from what I think was the new sensor and the new part, then fixed it by resetting the computer. About 300 miles later I had some bad hesitation during idle. It was the first time that I had gone to that particular gas station so I'm thinking that was it. I added fuel cleaner and it got better. I still have a slight hesitation during idle, much less than before. Is there anything else that could be causing it or was it probably just a bad case of gasoline?

Thanks

[Not Jo3L]

Have you put seafoam through the brake booster to help the idle?

It helped on my car for a few days lol

[el_Don]

No I haven't tried that. I'll try this weekend. Thanks