Certainlly engine braking in LFS atm is a bit extreme, when I raced saloons it was roughly 20% of the total braking force, in LFS it sometimes feels like it is the other way around.
Looking at the outguage data here is what we are imminently likely to get:
Engine Temperature (in degrees celcius)
Oil Pressure (in BAR's of pressure)
Currently these both send 0's, so aren't being used, but the memory and packet space for them is currently reserved in LFS - so they should be coming soon.
There's spare data slots in the outguage data too, so there's room for more stuff in the future.