Class B cabin noise, how much is too much?

I have a roll of sticky stuff that I use for a lot of different things. It's similar to adhesive rubber sold for picture mounting. When we first got our van it rattled and squeaked a lot. Had my wife drive around while I found them and marked them with tape. Then i used the sticky stuff, stick on bumpers and used screwdrivers to tighten things. I got rid of a lot, but some panels wouldn't stop making noise until I pulled them off and put insulation behind them to stop the flexing more than soundproofing. Some of those panels would just flex enough to make a noise, but only when driving. Some just made a little squeak of interior part on metal of the van.
It took a while, but I got rid of about 80% of the noises. Some still elude me.