Pedro Feliciano was stunned to see two Houston Astros with a combined three homers this season take him deep in the 10th inning.

The way the year has gone for the Mets’ bullpen, it shouldn’t have been surprising at all.

Brad Ausmus led off the 10th with his second homer of the year, Darin Erstad connected for his third three batters later and Houston rallied against New York’s unpredictable bullpen for a 6-4 win yesterday.

“I surprised myself because of giving up a slider for a home run,” Feliciano said. “We got struggle time, we got outstanding time. Just one day, one game. Tomorrow we’re going to come back and win.”

While Aaron Heilman failed to hold a 4-3 lead in the seventh provided by Carlos Beltran’s two home runs, and Feliciano (2-4), the Mets’ sixth pitcher, gave up both home runs in the 10th, Houston’s pen retired the 12 batters it faced to help the Astros improve to 3-3 on their seven-game road trip.

Chris Sampson pitched two innings in relief of Randy Wolf, LaTroy Hawkins (2-0) worked a 1-2-3 ninth and Jose Valverde was perfect in the 10th for his 33rd save in 39 tries.

Hawkins has not given up a run in 10 outings since Houston acquired him in a trade with the Yankees on July 30. He had a 5.71 ERA with New York.

“The bullpen has pitched awfully well. Now we can use Sampson along with Hawkins in the late innings,” Astros manager Cecil Cooper said. “I can’t say enough about them and the bench.”

Hunter Pence hit a two-run shot, but much of this win could be attributed to the substitutes, who’ve been pushed into bigger roles with Carlos Lee and Kaz Matsui out with injuries and slugger Lance Berkman playing sore.

Second baseman Mark Loretta made an elastic catch to end an early bases-loaded threat and had a sacrifice fly. Pinch-hitter David Newhan drove in pinch-hitter Geoff Blum to tie it at 4 in the seventh. Ausmus entered as a defensive replacement and homered in his one at-bat.

And Erstad was playing first base because Berkman was given the day off after a night game to rest his sore left hamstring and a jammed thumb, although he batted in the 10th.

“Terrific win. Team effort. Everybody contributed. We played them all and they all contributed,” Cooper said. “All our extra men played and lots of them helped out.”

The NL East-leading Mets lost consecutive games for the first time since August 10-11.

“We’ve played good baseball. We just haven’t got the offense on track in the last couple of days. They’ve done a good job against us,” manager Jerry Manuel said. “Their ‘pen shut us down and we kind of gave it up in our ‘pen.”

Manuel turned to his relievers after Oliver Perez walked Pence with one out in the seventh, and the Mets’ bullpen reverted to its struggling ways after showing signs of stabilizing during the first five games of a seven-game homestand.

Heilman gave up a double off the right-field wall to Blum on his first pitch. Newhan singled to right to drive in Pence, but Blum was nabbed trying to score. Fernando Tatis’ throw to catcher Ramon Castro beat Blum by several feet to keep it tied at 4.

Heilman, who hadn’t allowed a run in four outings, did not move from the stretch position while Manuel made the walk from the dugout to replace him with Scott Schoeneweis.

“It’s a tough deal because you’d like to see him attack,” Manuel said. “There’s also a plan in place and he didn’t execute.”

Beltran gave New York a 4-3 lead with his second homer of the game, a drive off the screen attached to the left-field foul pole. Beltran, a switch-hitter, had hit just two of his 17 homers from the right side before connecting as a righty twice against Wolf. It was Beltran’s 24th career multihomer game and second this season.Beltran’s first homer came after David Wright walked in the first.