We noticed the intake gaskets were leaking on cylinders 3 and 4 on the Lycoming IO-320 in an RV-9A. There was a logbook entry by the owner/builder for having replaced them. They were in fact installed improperly, preventing a proper seal.
As you can see from the pictures, the gaskets were installed on the lower side of the flange, instead of between the flange and the cylinder. This not only causes leaks, but will also cause the cylinder to run lean.