Perhaps I'm really out of it but I don't think you'll be troubled by the
"Border Patrol" unless you're smuggling illegals.  They work for the US
Immigration folks.

The folks who will want to look in your van in detail are US Customs Agents.
They worry about what non-human items you might be smuggling.

FWIW don't ever lie to one of these folks.  Answer succinctly and
pleasantly.  Volunteer no information unless asked.  The collection of
questions they ask will astound you, but believe me they are all relevant.

Note the badge number/IDs of the folks who search your car.  Just for
reference.

If you're hiding the PC show 'em.

I use a little form that you can pick up at any international airport that
declares what you took out of the country by item and serial number.  Coming
back in, presenting this paper gives an indication that you know the rules
and are trying to comply.

If any items are stolen whilst abroad, the paper helps a bit on insurance
and recovery.

On a motorcycle trip to Canada, entering at Vancouver, the local Customs
fellow detained me for two hours while they searched my motorcycle and
luggage for whatever it was they were looking for.  My companions also on
similar motos were not questioned.

Random search I suppose.

pensioner