Here’s a tidbit of info on what I’m reading on the ATF NFA Wiki…
If caught with a suppressor or ANY NFA item that you haven’t paid the tax stamp for, you’ll not only be subject to the state’s laws concerning owning the item and it not being registered (or in a state that bans it outright), but also will be subject to tax evasion penalties which fo this would be up to five years in prison.
So have at it pitman, make a few oil filter suppressors.