Hmm, well normally I would have a look at it to see what it could be ,but I barely have time to test my own mod at the moment. It will be for some other time. Just a couple more questions:
- Synch errors are not always caused by the mod itself. I don't know how you tested or with who, but do you also get a synch error without the mod installed? If not, then it still doesnt mean the mod is the problem, it could also be that there is a file(s) on the persons version who you are testing with which is not on your version of the game. Above all, you need to ensure that you both have the same version to build the mod on ( including custom m3D maps,autosaves,unorthodox changes to any of the game files, knowingly or unknowingly.
Only then one can assume the problem is with the mod, and to be honest, I don't believe it to be a problem with the mod, because the changes you have done, are not drastic enough to cause synchro errors when playing online, IF both players have an identical installation.
I know this may sound like ' yeah, I know this Angel' but guess what, it happened to me aswell when I did tests on my mod with Daddio. Constant synch errors, nearly giving up, thinking, this will never work, untill you go trough the installation again and come to the conclusion that the test mod was installed over a previous version.
[Maybe the game tries to go online to simcity 4 
--> Check your mod files, quite funny, there's an internet shortcut in your mod to it, though I dont believe this is at the root of the sync]
On the engine problem I can't speculate, just don't know enough about DN. Don't know what changes they did to the dmcr to speculate what might be going wrong.
