After several hours of running with a Scythe Gentle Typhoon AP-15 (58.x CFM), I saw a performance slowdown of roughly 8%. While I had thought the airflow coming from the front of the Cube was similar to the stock fan, it was noticeably warmer air coming out.

So, I used twist ties to attach another fan to the front. The result is hideously ugly, louder, but still much quieter than the stock fan, and is definitely putting out more air flow. It still feels warm, but I'm not using thermometers to measure this stuff.

There is also zero back flow out of the back where the fan is supposed to go. With both the stock fan and my Scythe replacement by itself, I was getting some back flow.

So far, my missing performance is back.

I'd appreciate anyone's insight on all this.