2000 Chevrolet S-10 - recurrent P0410

I am the original owner of a 2000 S-10 with 187,000 miles. Several months ago my check engine light came on. My OBD showed a P-0410 code. Being that this was the first time my check engine light came on EVER I took it seriously. The code was for the engine secondary AIR system that is supposed to be active only, if I understand it correctly, upon engine start up until the exhaust warms up. Since I knew everything was 19 years old I ordered and replaced everything not wanting to do it piecemeal. I replaced the air pump, hoses. vacuum check valve, diaphragm valve, the relay, solenoid valve, even the O2 sensors.
After the work was done I reset the code and all was well. At 186 miles later upon exiting the freeway after a 74 mile high speed drive the check engine light returned with the same code. I reset the code again and it returned again after another freeway drive. I live and drive in sunny Phoenix so rust, moisture and corrosion is not a concern. Any thoughts? Thanks for any response you may give. What am I missing?