Originally Posted by oldbogie
Check the flatness of the castings of the main body and the metering block in particular. These often warp, when rebuilding with fresh gaskets, early on things appear normal, but as the gaskets flexibility ages away then tiny air and or fuel leaks develop.
Hadn't thought of that. That sounds like what might be happening. Is there a way to fix this if that is the problem? What about doubling up on gaskets?