98 Integra RS with a lean spot

Hey all! I have an Integra that got dyno'd last year. The results were a bit disappointing - not so much in overall output as the wacky torque and AFR curves.

A picture to demonstrate:

Dyno Graph

This is a 98 Integra RS (as you may have guessed   ). It has an AEM V1 CAI and an Apex'i WS II cat-back. Not major mods by any stretch of the imagination. As you can see there's a MAJOR lean spot after the infamous AEM torque hump. The torque stumbles a bit too. There's a definite "softness" to acceleration in this range too.

I have heard all kinds of ideas on why this is. Sure, the torque hump is normal but I've seen other CAIs that don't have 1000 RPM lean spots. O2 sensor has been suggested (doesn't seem likely at WOT though). Valve lash? Maybe a wonky FPR (I changed out my fuel filter after this)? Any suggestions are definitely welcome.

I know Turbo had a CRX with a similar issue that was cleared up by installing an intake manifold with shorter runners. I don't remember which issue it is offhand - I think it was about a year ago though. if someone can point me to that I'd like to buy a back issue if they're available.