Currently in BeamNG, when you drive a modern diesel car like the Cherrier or the ETK 800 / K-series, and you remove the exhaust, there isn't any diesel smoke. In real life, a car like this would produce black smoke when the diesel particulate filter (DPF) is removed. So my suggestion is that they give the player the option to remove the DPF from the exhaust system. So when this is done, the car will produce some black smoke, and the engine performance will be somewhat affected. It's a small suggestion, but I think it makes the game just abit more realistic.