Im new to Hondas and I recently got a pretty much stock 00 Si. Its got a lot of miles (18X,XXX,) but it was running great until this morning. I let it warm up properly and was just driving around normally, but then gave it a quick run through the gears when provoked by some jack ass in a dodge ram. Shortly after I noticed the engine was obviously misfiring. I took it to Advance Auto parts to read the now flashing Check engine light. It threw 1. Random missfire, 2. Ignition system missfire, 3. Down stream o2 sensor, and 4. Emission system control something or other. The last two have been on since I bought it do to an aftermarket cat back. I replaced the plugs (NGK R v-groove,) wires (replacement,) cap and rotor also stock replacement. While I was swapping them I found what I thought to be the problem in that the rotor had some of the plastic ribs broken off and sitting in the cap. BUT when I started it up and let it idle it is still shaking and the check engine light is still flashing. I also just changed the oil with Valvoline Max Life yesterday, its not leaking and the level is normal. ANY IDEAS? sorry so long just thought Id clear up some things I figured I'd be asked.