hi, I have a 98 civic ex coupe d16y8 5spds with 167,000km, aem cai, catback exhast. my engine threw a CEL today with fuel running too rich. Anyone know what could be wrong? Could my EACV (electronic air control valve) cause to throw a cel? Honda said it might be the fuel pressure regulator, but other mechanics said it would be something else, most likely not the regulator. Any idea? Please help.

Also my rpm had been weird lately, everytime i go into neutral, the rpm would drop to like 800rpm, then jumps back up to around 1150rpm then would go back down to around 800rpm.
Is this normal or is there something wrong with it.

I had replaced the following part,

Primary / secondary O2 Sensors
Map sensor
TW sensor
Resonator
Alternator
Spark plugs and wires

Thanks you!!