When the Movex truck is in the middle of the street, the police car turns and the driver-side window is down. The next scene when MacGyver almost hits the police car, the window is up. Apparently it's down again when Pete yells that MacGyver has less than 5 minutes left.
When Mac pokes the hole into the can of yellow paint it lets off a steady stream of paint. He then crawls from under the vehicle, directly under the paint can, and somehow doesn't get any paint on himself.
The slumped head of the "dead man" in the chair visibly tilts to the other side, even though there is no "outside" movement to make it change position. Obviously the man in the chair is the real live actor instead of a look-alike dummy, and he simply moves his head a bit to get more comfortable while still pretending to be dead.
Stong's market is a Canadian grocery chain, but the bombed post office was a US Postal Service building.
Nikki doesn't seem to have any knowledge of the Post Office bombing, even though she had just left the location and should have heard the explosion itself or on the news.