Wow, thanks for taking the time to re-read the whole thread! :D. Great to hear that you're also an AE100 owner. Looking forward to seeing what mods you do to yours and am glad that mine has provided some inspiration :). Can definitely help with parts if you need them (H)
I came across some info online a couple of weeks ago about a few different people in Malaysia using a 6-speed ECU with their 5-speed Blacktops and noticing a slight increase in power/response, so when I stumbled across a 6-speed Blacktop ECU a few days ago for a good price I decided to test it out for myself.
The 6-speed ECU is meant to have better fuel mapping, better engine response, a raised rev limiter and a safety function which makes the engine idle up for a second when changing up or down a gear at a certain rpm, which helps to protect the 6-speed's synchro's and reduces driveline lash.
I swapped the ECU over today but before doing so took my car for a drive with the 5-speed ECU still fitted to see what my current rev limiter was before the engine would valve bounce. In 1st gear it was about 8,300rpm and in 2nd and 3rd gear it was 8,250rpm. After I installed the 6-speed ECU and went for a decent drive I tried it again and noticed that in all the gears I tested (1st, 2nd and 3rd) the rev limiter was now 8,500rpm. Prior to the swap I had heard that the 6-speed ECU would hit the limiter at 7,800rpm in 1st gear, but this wasn't the case in my experience (bearing in mind that I am however running the 5-speed C56 transmission).
The engine response does seem slightly quicker but nothing mind blowing, however the slightly increased rev limiter comes in handy when changing gear at high rpm as every little bit helps to keep it within the power band after shifting. The 6-speed ECU is also meant to be a bit more economical on fuel but I haven't been able to test that as of yet.
All in all it does have it's advantages over the 5-speed ECU and for the price I paid it was certainly worth it
These are some photos I took before the swap, with the 5-speed ECU on the left and the 6-speed ECU on the right: