'05 SE-R P300 - Multiple Cyl Misfire

[junejune0605]

I'm hoping and praying someone in here can help me.

I have been having this code for the past couple months (since I purchased the car) and I can't seem to get rid of it.

P300 - Mult. Cyl. Misfire

I have changed both of the pre cat O2 sensors because a mechanic friend said that the front bank was running lean and the rear bank rich and the O2 sensor in the front was showing a low reading.

Still having the same issue.

Here are the symptoms:

Rough idle.
If the vehicle sits for long enough, I hear a poof kind of sound come out the exhaust every 10-15 or so.
SES light will blink at times, disappear some other times, or stay on solid.