AFAIK, smoke at full power is quite documented on late war german acft, due to use of synthetic fuel that did not burn well. Now i don't have any old movie handy, but maybe someone can link one that shows the effet ?
Now IL2 defaut effects are quite poor, and this feature would need a better effect, but it's expected in a soon later release, if i read well
http://ultrapack.il2war.com/page/readme