Shea Hey Kids

The average number of runs scored in a game at Shea Stadium during the 2006 season (both teams combined) was 9.16.
The average number of runs scored in a game at Shea Stadium during the 2007 season (both teams combined) was 9.17.

The average number of runs scored in Mets road games during the 2006 season (both teams combined) was 10.16, exactly 1.00 run more than the 9.16 runs scored in Mets home games in 2006.
The average number of runs scored in Mets road games during the 2007 season (both teams combined) was 10.02, 0.85 more runs than the 9.17 runs scored in Mets home games in 2007.

In 2006, that exactly 1.00 run more scored on average in Met road games than in Met home games was divided almost evenly between higher scoring by the Mets and higher scoring by their opponents. The Mets scored 0.54 more runs in their road games than in their home games, and Mets opponents scored 0.46 more runs per game when playing the Mets away from Shea than in games at Shea. In short, in 2006, Shea was consistently and reliably tougher to hit in than most parks, with scoring by each team lower by about half a run per game on average at shea than in an average park.

In 2007, the 0.85 more runs scored on average in Met road games than in Met home games consisted entirely of higher scoring on the road by the Mets themselves. Mets batters in 2007 averaged 0.87 more runs per game on the road than Shea. But Mets pitchers actually allowed a tiny number of runs fewer on the road than at Shea -- Mets opponents averaged 0.02 fewer runs per game in games against the Mets away from Shea as compared to games at Shea.

So to summarize, in 2006 Shea was consistently a tough park to hit in, basically equally so for the Mets and their oponents. In 2007, Shea was still a tough park to hit in -- but only for the Mets (for whom it was even tougher than in 2006). For Mets opponents, Shea was a neutral park for hitting in 2007.