I've looked for posts regarding removing the middle muffler but can't find them.... so sorry if this is a repeat.
Has anyone done this and what were the results? (Noise levels, performance etc?)

 

Here in the states, we call it a resonator or pre-muffler, so thats probably why you couldn't find it. There have probably been 100s of post on this. Some like it some dont. I replaced mine 2 hours after I had it removed. It sounds great a WOT, but cold it is very raspy, and has a loud drone when motoring along at part throttle.

I replaced the aft muffler with a flowmaster 80 series though, the one for a camaro, and its a much deeper growl.

 

Good on ya mate!!
Thats what I wanted to know - I'll leave it alone. I wanted a better "growl" but can't stand drone at speed. I'll wait till someone does it here and I can listen. It doesn't always pay to be the first.

 

I removed mine and left it out. I don't mind the tone, sorta like it. there is more power, and the noise level is acceptable, and the tone is pretty good. However I'm planning on putting in a true dual system. I'd go Borla, but they don't make a system for a G35 and don't know if they will. I think I'll have a shop fab one up along the lines of the Borla. They use MagnaFlow Mufflers. Anybody know anything about their 2 in 2 out model.

 

You should replace your stock muffler w/ a flowmasters 80 series, Its sounds mean WOT (wide open throttle). I first removed the resonator, which was ok, but I couldn't really tell any differnce unless I had the window down. Once I put that Flowmasters on, it was a totally different storry, it is deep and loud enough, but not too loud to where its annoying. All of these mods are cheap, and shouldn't cost too much in labor, plus if you plan on going w/ a CAI system, it helps breath smoother.