My Service Engine Soon light has been coming on intermittently lately.

Under hard acceleration (like on the freeway in 4th or 5th gear) the acceleration isn't smooth (a little jerky). My friend said not to use Shell gas (which I switched from) and the problem (and the SES light) went away for a little bit... now the light and the same behavior is back.

Thing is I live in the bay area, and the coldest it ever gets here in the mornings is 40-41?F (and even thats rare).

I only use 91 Octane. Same problem you guys think?