So there's heaps of DIY smoke test machines demonstrated around the web.
I learned to built one of these, was kinda fun. It worked, even found a crack on my air intake that was messing with the fuel trims.
Mine burns pure mineral oil inside a paint tin using a fibreglass wick wrapped inside a nichrome wire coil that's designed to heat up when current passes through.
I've read articles where smoke testers are used on intakes, exhausts, evap systems and all sorts of lines and pipes.
But this got me thinking before using it much more. Is the smoke or residue from the mineral oil going to cause any problems to the cars sensors, fuel injectors or other components ?