Bill,
I'm an oldie here too from the past and (unfortunately) don't wander over here too often anymore. Frankly, one reason I stopped by was because that it seems like there are SO many Ford GT owners that have or previously have had NSX's. It's really an amazing statistic I believe.... but I digress.
I had the Basch installed on my NSX approximately the same time as you did. Through the school of hard knocks (no pun intended) I discovered that no one in the NSX community knew anything much about the SS box - and unfortunately not Mark (at the time). Over the course of approx. 4 months, I got to know the SS box quite well - and also had the good fortune to get to know Mark (owner of Split Second) pretty darn good.
With a considerable investment in some good wideband equipment and a lot of hours of careful tuning, I created more than 60 variations of SS mapping tables for the NSX. Mind you, during every step of testing, I was running 100 octane (as a precaution) and the wideband was both datalogging and providing real-time feedback. In my humble opinion, I think I ended up with absolutely the best tuned Basch SC on the planet. Seriously, my car ran very, very well.... and still does today for the new owner. BUT, it was completely unrealistic for your average owner to have to go through what I did to get the kit running as it should.
Also, since so much time has passed, I'm no longer reluctant to say things I wouldn't have said in the past. So, regarding the , replacement version of the SS Box, Mark Basch and Mark from SS were never in agreement that there really was a problem with box number 1. In other words, there might not be any harm at all to stay with the SS box you have in the car. (Again, I think most of the pengine problems were due to poor mapping tables.)
Another admission is that I'm not sure that Mark Basch EVER came out with a real good map. Honest to God, in all of my experience, I only heard my car ping one time, and that was the day that Mark had dropped the car off at my home and I took it for the first drive with the SC. In all of my testing and experimentation - we NEVER allowed the car to get itself into a lean ping condition. Anyway, at one point I know that Mark was distributing a mapping table that I developed (he denies it... and perhaps we iterated to the same table), but I made progressively better tables.
Let's get back to you post and quest for input:
1. Your coolant leak is coming from the polished aluminum overflow reservoir. I'm certain of it. These overflows were sourced from Dali back when Mark B and Mark J were still friends. The whole first batch of them leaked. Mine leaked. Mark B replaced mine and acknowledged that he had replaced several others. This is your coolant problem.
2. I wouldn't worry about installing the new SS box. However, I would update to a better map. If you can't get one from Mark or the gent's here, I'd be happy to go root around and see if I can find mine. I caution you, however, unlike Mark I do not claim that one size fits all. If you want my table, know that it works perfectly in my car. I would THINK that it would work well in your car BUT I DONT KNOW. Get back to me if you want.
3. There's an outside chance that I still have Mark's instructions on installing the new box. As I recall there's at least one non-straightforward wiring trick. By the way, on all of our early cars, Mark spliced directly into the ECU wiring harness. Along with the new box, I strong-armed Mark into giving me the short female/male ECU loom to make the SS box truly plug and play. When I installed the new SS, I restored all of the factory connections (solder, shrinkwrap, etc.) and installed the short pigtail for the SS.
Finally, let me know how I can help.
And back to my original soapbox, I hope to see more of you over on the Ford GT forums..... dare I call it the next generation NSX?
Peace.