Well, just had the AFE installed yesterday. I like it and if you compare it to the stock intake the airflow passages are much larger. It's a very nice set-up and works with my Glacier fuel filter. With everything I've done to my truck it's hard to tell if I've gained any additional performance. But, I replaced my turbo and went with an AFE stage 2, so I figured I'd replace the intake manifold as well. If anything, my turbo may spool a tad quicker and the egt's are a bit lower. I'm sure it's similar in performance to any of the other aftermarket intake manifolds out there.
Jacob