Generally speaking exhaust nuts rust/corrode more than anything else on the vehicle due to the extreme heat cycling. Also, Toyota typically uses exhaust nuts that have thread cleaners/cutters so that also makes them more difficult to take off. Try taking the nuts off when the exhaust is hot.Helping my neighbor with his rear 01 Tundra O2 sensor removal...are the rear nuts being VERY rusty something that is common ??...checked a Youtube video and the gentleman removing his is faced with this issue also !!