I wouldn't go above 4.1
Have you considered a lightweight flywheel?
If your NC is feeling 'sluggish' I'd imagine the lightweight flywheel would pep the car up quite a bit, increasing the throttle response making the car more 'zippy' through the gears.
Just a suggestion, if you couldn't tell I'm trying to talk myself into getting the flywheel soon.
I've heard nothing but great things so far, maybe someone who has a flywheel installed will chime in...
Anyways, good luck with whichever route you choose to go!
Well, look no further, I have the fidanza flywheel installed just a few months back
It was a fantastic purchase which I have no regrets. Some of the concerns I had when I was getting the flywheel was that the fidanza might be too light, and makes daily driving a chore. Another would be the fly wheel chatters that some mentioned about.
After installation, this is what I find. The rev does goes up faster but it drops faster too, initially driving was pretty jerky but once you get used to it, the drive is so much better than before. One tip I can share is that you need to learn to blip the throttle during downshift (heel-toe) as well as upshift to make the transition smoother. PM me if ya need more details
As for the chatters, I have been driving for 3 months now, and I must say there are hardly any chatters except the sound of the engine rev-ing. It all boils down to the guy installing the flywheel, take note never to use pneumatic tools to tighten the flywheel, mine was installed by the old mechanics who tighten everything with a hand tool and was being very careful to ensure the alignment was right.
As for the changing of 6 speed to 5 speed, I think that's a little impossible for me, now that I know better.
Reason why I gotten the six speed was due to the LSD and bilstein, but as you can see, i have changed both of them. I have also heard that the 6 speed gear box is better suited for track, but oh well.
I am also thinking it will be easier to sell my current FD 4.1 with Stock LSD as a package for all those guys running on 3.7 without LSD in Singapore, rather than just selling the stock LSD alone. Oh well, more guys to chip in on this topic please?