I've tried a K&N filter in the factory air box, a Tymar and now a A.I.S. with the foam air intake sleeve.
I liked the Tymar for the performance and sound. But I found that because it inhales heated, underhood air, the EGT's ran a bit higher and the cooling fan cycled more frequently.
After switching to the A.I.S. w/Zoodad mod, the EGT's were lower and possibly the boost levels at cruising speeds were slightly lower, but I can't say I'm 100% sure about the lower boost. The cooling fan didn't cycle as often also. The restriction indicator would move slightly only under full throttle, so I added the foam intake sleeve. The restriction indicator hasn't budged a bit since.
In summary, I thought the Tymar was ok for non-towing situations. But since the huge majority of my driving was with a trailer in the rearview mirror, the A.I.S. /foam intake sleeve combo was the best way to go.