As an addendum to my above post (yes, I've been thinking about it), unless/until you're ready to go to Hoosiers (or comparable) I'm not convinced significant suspension improvements will do you too much good.

Example: in my original build on the NX2000 (c. 2002) I slapped on KYB AGX shocks and standard-issue street spring rates (350F/200R?) This was during my "listen to the Nissan experts" phase...anyway, key note is that I was running Kumho Victoracers...one of the first tracks I drove was Lime Rock Park, and after some testing I was able to get that car down to the 1:03's.

Soon thereafter we switched to Hoosiers. It didn't take long to recognize we needed more spring rates on the car to both control the geometry and keep it off the bump stops. Of course, as we added more spring rate we needed better shocks. We went from those crappy AGXs to some Advanced Design struts (another one of those "listen to the experts" things) and then later on to Kessler-fabbed 8611-based struts. Strangely enough, even with all those improvements - including a new very stiff cage to replace the old bolt-in Showroom Stock one - it took us until 2006 to get the car down into the low 3's, eventually into the 2's...

This was always one of those things that totally perplexed us. Had we bent something we can't find? Had I suddenly recognized my mortality and was driving worse? Was it true that maybe AGXs were a better package for this car? Nope. What it most likely was was that with the lesser grip of the Kumhos we weren't getting nearly the lateral g-force as from the Hoosiers, and as such simply didn't need to control the suspension geometry nearly as much. In effect, without the lateral forces of the Hoosiers we simply weren't getting into that nasty negative-roll center and suspension-bottoming area that we found ourselves in when we Went Purple.

So, this makes me wonder if maybe it isn't time for some soul-searching on your part. If you're going to hang with your current selection of tires, I'd suggest you need to maybe tune some things around without massive changes. I'd suggest your 8611 are fine as-is and maybe we shouldn't look into seeing how the suspension is working with the current grip levels. Then, once you're ready to make the Jump to Purple we then start delving into significant springs, shock, and bars changes... - GA