Because I wanted to be properly armed minutiae-wise for my travels, I did some studying on Baseball-Reference.com and BaseballMusings on previous Mets voyages to The Steel City, and here's what I've gleaned.
* The Mets are 316-350 all-time against the Pirates, with 146 of their victories coming in Pittsburgh. The all-time record is slightly misleading, because if you subtract the first five seasons in Mets history, the club is 295-281 against Pittsburgh. That's pretty good considering they started 1-10, 2-20, 5-30, and 8-40 against the Pirates.
* Only two players have had a .400 or better batting average for the Mets against the Pirates (minimum 50 plate appearances). If you guessed that the pair were Rico Brogna (.414) and Dave Gallagher (.409), you're not only correct, but amazing, and should probably be writing your own blog.
* The most home runs by a Met against the Pirates is 34, by Darryl Strawberry, a whopping 13 more than runner-up Dave Kingman.
* Only one Met has had a five-hit, two-homer game in Pittsburgh. That was done by Mike Piazza on April 14, 2000. Dave Kingman (3), Willie Montanez, Mark Carreon, and John Olerud are the only other Mets with a multi-homer game in Pittsburgh. Tommie Agee is the only other Met with a five-hit game in Pittsburgh.
* The most wins for a Mets pitcher against the Pirates is 21, by both Jerry Koosman and Tom Seaver. The most wins for an unbeaten Mets pitcher against the Pirates is 4, as both Tom Glavine and George Stone have 4-0 records against Pittsburgh as Mets.
* The complete-game shutout has indeed gone the way of the dinosaur, particularly when it comes to throwing one on the road. The last Met to throw a complete-game shutout in Pittsburgh was David Cone, on September 29, 1989. In fact, the Mets have had only one other shutout in Pittsburgh since that game (May 9, 2000). Cone is also the last Mets pitcher to strike out 10+ in Pittsburgh, which he did on October 1, 1990. The only other Mets to strike out 10+ in Pittsburgh are Tom Seaver (3 times) Sid Fernandez, and Nolan Ryan.
* It appears that the Mets have only had two players who were Pittsburgh natives- Frank Thomas and Don Shaw. If we include managers, you can add Art Howe to the list, though I prefer to forget him.
* Among the unique things that have happened involving Mets trips to Pittsburgh: A September 12, 1969 doubleheader in which the Mets won each game 1-0 and the winning pitchers (Jerry Koosman and Don Cardwell) drove in the winning run in each game; a walk-off loss on August 8, 1974 interruped by the announcement of the resignation of president Richard Nixon, and an August 6, 1988 matchup in which the Mets were the recipient of three balk calls in the eighth inning of an eventual 5-3 victory over the Pirates and their closer, Jim Gott.
* 93 players have played for both the Mets and the Pirates in their careers, a list that includes Moises Alou and Gary Matthews Jr. among others, though I'd forgotten that either played for Pittsburgh. Of those, four played for only the Mets and Pirates, with that quartet being household names Steve Bieser, Larry Elliott, Larry Foss, and Tom (traded to Houston for Jerry Grote) Parsons.* The Mets are 39-30 all-time in games against the Pirates that were decided by walk-off, but only 1-1 since 2000.