I am having trouble shifting in/out of forward and reverse and I think my engine rpm might be the fault. It is idling at around 1575-1600 rpm. Is there a external idle adjustment screw on the EFI or is it controlled by the ECU?
Its all efi controlled by the ecu. Do you have aftermarket exhaust or intake restrictions? Is the cable going to the peddle tight when your not touching the peddle? If that nut assembly got tightened some how then it may be pulling on the throttle at idle.
I had the same exact problems with my 2013 RSX just after I bought it last summer with less than 20 miles on it. I took it back to the dealer a few times they tried several things including replacing the primary clutch and I still had the same problem until they replaced both the primary and secondary clutch I now have almost 700 miles on the machine and have not had any more problems. That would be my suggestion for a fix
The Idle you are talking about is way too High..Your Iac could not be working correctly..Mine Idles down to 850 RPM and have no Problems with shifting at this point...Sometimes an easy fix can be..is to take the iac off and simply use Carb clean and clean it...Also take the negative cable off the battery and wait a couple of minutes then Jumper it to the Positive Lead momentarily to reset KAM//Keep alive memory/ and that reboots the ECM and make it relearn the parameters