THe other day my 01 IS threw the 300 code. I changed the plugs and now it seems to be fine but it still starts up a tad rough for a second. I have done nearly everything I can recently to this car. New plugs, plugs wires and coils, O2 sensors, Timing belt, VVTI, It isn't throwing the code now but I am worried it is like on its last leg or something major is going to happen. It just turned 230k. Any suggestions. Did not look like I have a head gasket leak from the plugs.

 

Little bit over reaction. Did it give the P0300 before the changes? Plugs, wires, coils, Coil connectors, etc.... Need more details.