From the way things look im thinking the new 2006 si is going to need 91 or higher fuel to run properly? I hope im wrong as I would rather see the compression dropped alittle and sacrifice a few hp so I could run regular unleaded. I built a couple motorcycle motors and come to the conclusion the 1 point in compression ratio just doesn't add up to much more performance just higher fuel bills. On a side note I been driveing a 2000 civic ex since new and find it to be a great car. My only disapointment is I didn't opt for the si version.