Hey I had some similar issues you described (misfire codes, lean at idle, etc) and ended up replacing the fuel rail pressure sensor. Technically, Mazda says to replace the whole rail, but I just replaced the pressure sensor and it's been fine almost 20k miles later. See this thread for the fix...
Hi all! I wanted to share my experience as it was fairly rare and I found a fix that worked.
I bought a new to me 2007 Mazdaspeed3 with approximately 170K miles in August. It was a 1 owner, completely stock car (unicorn, I know).
When I bought it, it was having some misfires. I assumed this...