I know it's been like 11 years since this post and you probably don't own the car anymore. I was wondering if you ever resolve this issue or know the cause of it? I'm having the same exact codes (301, 303, 305 all the back). I just had the coil and plugs changed about 2 months ago with Denso coils, and I recently changed the 02 sensor by the radiator and PVC valve. I'm going to check whether it's the spark plugs used to see compatibility. Fingers crossed.

Pending - P1130 (Bank 1 Sensor 1)
Current - P301, P303, P305 misfire