So I am getting my RSX back up and running after 2 years of sitting. It seemed to run well after I replaced the o2 sensor but tonight had 5 pending codes p0300-0304 for misfires. I also have an validated code of p1457 which is an egr type code that came up the other day. The car runs great when you are low RPM or low throttle but if you get on it hard it starts to stutter and have misfires. I am thinking of starting out with new spark plugs and running some seafoam through the system. Any advice on how to start running down this problem?