Adrian Sutil continued Force India's excellent weekend by topping a second straight practice session at Monza.
The German, who had also been quickest on Friday afternoon, beat championship leader Jenson Button's Brawn to the top spot in the final practice hour.
It was an encouraging morning for Brawn, with Button's teammate Rubens Barrichello fourth behind BMW driver Nick Heidfeld.
The McLarens completed the top six - early pacesetter Lewis Hamilton 0.2s quicker than team-mate Heikki Kovalainen - ahead of Tonio Liuzzi, who was an impressive seventh in the second Force India.
Most of the session was dominated by the men who had set the Friday pace: Hamilton and Sutil.
The McLaren driver emerged on top of the first runs, then chipped away at his time further with every outing, eventually reaching 1m23.929s on soft tires with 20 minutes to go.
Sutil, still on hard tires and up to second by this time, looked set to beat that benchmark until a mistake at the Ascaris cost him a few tenths. He quickly shrugged the error off, though, and improved to 1m23.735s to depose Hamilton next time.
The German went faster still when he grabbed soft tires right at the end, lapping in 1m23.588s first time around even though his first two sectors were not an improvement on his hard tire time.
That meant there was still more speed to be found, and although Button briefly grabbed first place away with a 1m23.404s, Sutil came through to beat the championship leader by 0.068s moments later.
Giancarlo Fisichella's difficult Ferrari initiation continued. For the second session in a row, the Italian was at the foot of the timesheets - but this time because he had slewed off the road and crashed into the tire barriers at the Parabolica just before the session's halfway point.
Renault's Romain Grosjean was responsible for the other spectacular incident of the morning, as he misjudged the approach to the Ascaris and took a wild - and briefly airborne - detour over the grass.
Grosjean still managed 11th place, 0.3s and three places behind team-mate Fernando Alonso, with Timo Glock (Toyota) and Robert Kubica (BMW) between them.
Kimi Raikkonen was only 12th for crowd favourite Ferrari, while Brawn's title rival Red Bull saw its driver Mark Webber and Sebastian Vettel manage only 17th and 18th places as they again ran less than most other teams.
Jaime Alguersuari also missed a lot of mileage for the sister Toro Rosso team, the Spaniard being sidelined by a gearbox problem.
Pos Driver Team Time Laps
1. Sutil Force India-Mercedes (B) 1:23.336 21
2. Button Brawn-Mercedes (B) 1:23.404 + 0.068 21
3. Heidfeld BMW-Sauber (B) 1:23.490 + 0.154 18
4. Barrichello Brawn-Mercedes (B) 1:23.575 + 0.239 20
5. Hamilton McLaren-Mercedes (B) 1:23.633 + 0.297 18
6. Kovalainen McLaren-Mercedes (B) 1:23.803 + 0.467 20
7. Liuzzi Force India-Mercedes (B) 1:23.849 + 0.513 21
8. Alonso Renault (B) 1:23.915 + 0.579 17
9. Glock Toyota (B) 1:23.959 + 0.623 21
10. Kubica BMW-Sauber (B) 1:23.996 + 0.660 18
11. Grosjean Renault (B) 1:24.197 + 0.861 15
12. Raikkonen Ferrari (B) 1:24.302 + 0.966 20
13. Trulli Toyota (B) 1:24.326 + 0.990 17
14. Nakajima Williams-Toyota (B) 1:24.392 + 1.056 20
15. Buemi Toro Rosso-Ferrari (B) 1:24.572 + 1.236 23
16. Rosberg Williams-Toyota (B) 1:24.621 + 1.285 21
17. Webber Red Bull-Renault (B) 1:25.154 + 1.818 13
18. Vettel Red Bull-Renault (B) 1:25.244 + 1.908 16
19. Alguersuari Toro Rosso-Ferrari (B) 1:25.791 + 2.455 10
20. Fisichella Ferrari (B) 1:25.951 + 2.615 10
All timing unofficial