A part wear/performance drop/failure, should be added. It will only contribute to LFS realism and enjoyment, we all know that if in real life, we can't keep pushing the engine to it's limit all the time, to preserve the integrity of the car components is a very important part of the racer strategy, we can try to earn that extra points in a race, but we know that we are going to risc the equipment, or we may be confortable with our position in a race, and start saving the equipment. It should be very well implemented, and adjusted, to prevent LFS to loosing or disapointing it's public...
I wonder we could have a beta patch soon, so we can start helping to develop and adjust a wear/performance drop/failure system.

I think the keywords to the engine tunning/tweaking question are: DAMAGE, RELYABILITY and CONSISTENCE. A agressive tuned engine will not last long and will be harder to drive. Maybe the damage system will have to act in long term, the engine could crash after... don't know... 4 races? 2 races? that will depend on the engine tunning and most important, the way the driver uses the engine. If you overrev the engine, you may improve your lap time, but you are going to raise your engine temperature, and reduce the life and maybe the performance of the engine components... I think even if no engine tunning is implemented, the engine damage system have to be improved, for instance, you can put in neutral or hold the clutch, drop the hammer on the gas pedal, stay like this for the all day, and nothing but running out of fuel will happen, even the engine temperature won't change. I think a realistic engine is a must-have in LFS, the best car simulator ever!