This is the first time I've seen this code, which doesn't surprise me since I don't deal with newer cars. Here's a caution - I don't know your car worth a lick.
P1520 - Inlet Manifold Runner Control malfunction.
You didn't get the IMRC failed open or failed closed codes, so your problem (at least right now) isn't significant. Chances are that at higher throttle (above ~3500 rpm), you may be getting mildly erratic performance. You PCM tries to efficiently admit air to the intake by using two different modes (low rpm and high rpm). Your problems relates to the PCM seeing an unexpected voltage signal above ~3500 rpm.