Yes, I am happy with the jacobs set-up, it was the second upgarde, the K&N FIPK was the first. As with all of the 3.0 upgades none of them are profound increase in performance and power alone. With the Jacobs you do get better throttle/rev response, better mpg, and lower emmissions. I do notice a difference in performance when I have had the Jacobs disconnected, (I have had to replace the coil twice and the cpu once over the last 10yrs).

You can cut holes in the oem air box(on the bottom) to help it breath easier, this would give you an idea of how the after market intake systems would help. If don't want to cut on the box, you can remove the drivers head light and drive it around a bit and see if it performs better.

How open is the magnaflow mufler, I found with an open muffler I lost too much low end torque with my 3.0 and a heavy truck. It was great if I wanted to run in the hi 4k's or run the truck past 85mph in 4th, but it wasn't much fun driving it artound town or on the trail, and my mpg's suffered.