DC9; DC16

[bamers]

I feel bad for your situation,
it must piss you off

Getting disconnected during races is the worst

I had similar problem, however it was when I was using the university's wi-fi
So I connected, and use a VPN, however, I got many disconnect problems which caused me to get timed-out when playing on NFS:SA
and at the end, I just gave up using university's wi-fi

I tried also to connect and play on other servers in MTA, even SAMP, none of them gave those problems

I didn't know for sure the reason, but most probably caused by the huge size of resource used by NFS:SA and/or 

BUT, since you mentioned that you already tested playing BIG servers too,
well, I am sorry, I can't find any better information for the solution of your problem

maybe make sure that your internet provider stability AND your OS has no problem in the data package delivery of both directions
also check any software that may interfere your PC's communication with the NFS:SA server's address

that's the best I can think so far,
I hope I can be any of use