Ex-Formula 1 driver Monteiro moved to the head of the 29-car field a third of the way into the half-hour session, before Chevrolet driver Huff improved on the Portuguese racer's effort by 1.028 seconds with 12 minutes left on the clocks.
Monteiro narrowed the deficit in the closing minutes, but seconds before the chequered flag Huff produced a blistering lap of 1m31.899s to cement his position.
Alain Menu, second in the standings some 35 points adrift of Huff, was third fastest ahead of RML Chevrolet team-mate Yvan Muller.
Yokohama Drivers' Trophy points leader Norbert Michelisz edged out fellow BMW racer Mehdi Bennani by 0.159s to take fifth spot.
Gabriele Tarquini claimed seventh place. The 2009 WTCC champion is beginning the final weekend of his seven-year SEAT stint before moving to JAS's Honda programme.
Michelisz's fellow Independents' class contenders Stefano D'Aste and Pepe Oriola were closely matched, finishing practice one in eighth and ninth.
Former Japanese single-seater driver Kei Cozzolino continued a slightly fraught acclimatisation to the WTCC. The Italian crashed his ROAL Motorsport BMW before setting a time, and limped back to the pits with a broken front-right wheel and numerous bent panels.
Pos Driver Team/Car Time Gap 1. Rob Huff Chevrolet 2m31.899s 2. Tiago Monteiro Honda 2m32.033s + 0.134s 3. Alain Menu Chevrolet 2m32.870s + 0.971s 4. Yvan Muller Chevrolet 2m33.060s + 1.161s 5. Norbert Michelisz Zengo BMW 2m33.319s + 1.420s 6. Mehdi Bennani Proteam BMW 2m33.478s + 1.579s 7. Gabriele Tarquini Lukoil SEAT 2m33.828s + 1.929s 8. Stefano D'Aste Wiechers BMW 2m34.235s + 2.336s 9. Pepe Oriola Tuenti SEAT 2m34.378s + 2.479s 10. Franz Engstler Engstler BMW 2m34.812s + 2.913s 11. Tom Boardman Special Tuning SEAT 2m34.961s + 3.062s 12. Tom Coronel ROAL BMW 2m34.994s + 3.095s 13. Fredy Barth SUNRED SEAT 2m35.096s + 3.197s 14. Darryl O'Young Bamboo Chevrolet 2m35.370s + 3.471s 15. Alex MacDowall Bamboo Chevrolet 2m35.437s + 3.538s 16. Andre Couto Tuenti SEAT 2m35.694s + 3.795s 17. Charles Ng Engstler BMW 2m35.939s + 4.040s 18. Tom Chilton Arena Ford 2m36.505s + 4.606s 19. James Nash Arena Ford 2m36.831s + 4.932s 20. Fernando Monje Tuenti SEAT 2m37.543s + 5.644s 21. Aleksei Dudukalo Lukoil SEAT 2m37.966s + 6.067s 22. Filipe de Souza China Dragon Chevrolet 2m41.670s + 9.771s 23. Kin Veng Ng China Dragon Chevrolet 2m42.842s + 10.943s 24. Celio Alves Dias China Dragon Chevrolet 2m42.927s + 11.028s 25. Eurico de Jesus Five Auto Honda 2m45.512s + 13.613s 26. Jo Rosa Merzsei Engstler BMW 2m45.638s + 13.739s 27. Ka Lok Mak RPM BMW 2m46.818s + 14.919s 28. Kei Cozzolino ROAL BMW 29. Henry Ho Five Auto BMW
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