I just purchased a year 2000 Honda Accord SIR with the F20B DOHC engine out of Japan equipped with Mugen Rims and the Mugen headers 4-2-1 ..The headers fit perfectly into the existing exhaust ststem ..I am experiencing a problem with this car and have been unable to contact Mugen for advice....At approx 50-80 rpm above the recommended idle for this car with the airconditioning on and the the transmission selected the exhaust pipe vibrates from the cat to the first pan..Its really irritating..It is very reduced with the A/C off...The idle speed is correct..The mounts are perfect....The air conditioning pressures are spot on...
If you need anymore info I can provide it...Will really appreciate any info you can get from Mugen..Repeating A/c on and you are coming to a stop the exhaust vibrates between 50-80 rpm above set idle and you feel it throughtout the car...The engine is the DOHC F20B...

P.S. Fuel Injectors and throttle body was cleaned..Mileage 40,000 kms

what is an F20B that sounds like an interesting engine. Does anyone know what kind of power you get with that engine. is it worth swapping in and losing some displacement? is it good to turbo?