Don't expect a lot from Denso, but have to try.
The ECU from you has been donated to this project - 
, if you need one let me know - will replace. Not to be a hoarder, but have three other operational ECUs - the original, spare I bought, plus the one that came with the 1200 carcass out of Ontario. The interesting part about these ECUs is that the engine operated the same regardless of which one I used - no fast idle, and a disgusting fuel smell on first start in the morning. Since you cannot change/vary any ECU parameter/setting, timing, fuel mixture and such cannot be changed and the issue will never go away. I expect that the 1800s will have issues as time goes on, but its FI system is more modern - is there an O2 sensor on the 1800?
A fellow I correspond with on the Facebook SE-i and Limited Edition forum, has an '85 Limited Edition, his second in about as many years, and he has a fuel mixture and idle issue. He wants to adjust the TPS to try and get rid of the issues but this has not been my experience.
I think I mentioned that Pim on the CX500 forum has been trying to fix/mod/change CX650 turbo CFI ECUs but has had little success. He is looking at the Speeduino, and other ECUs I suspect as replacement ECUs.
As I mentioned above, replacing/modernizing CFI components that are known to work with a specific ECU is a good consideration at the start of a project such as this. Trying to make an old design work with newer technology can be a stumbling block preventing real progress.
These Limited Edition and SE-i models are very robust and keep going, and going as you mention. It's when an issue occurs that people tend to think about bailing. Most owners will never attempt a project such as this, but as a retired old gentleman, can't leave this stone unturned. Should have an alternative part/component available just in case.
Long answer to your post.
