The sleeve should be sitting flush with the top of the engine head. If it got bumped up and turned it may not be able to drop back down. Many sleeves are keyed to only fit one way. Also, did you reinstall the brass shims? Is the glow plug tight? The head should be tightened tightly and evenly in a criss-cross pattern to ensure even tightning. Overtightnig should not warp the head unless the sleeve has bumped up or you tigntenen in an odd patern. Normally the only effect overtightening will have is that you risk breaking a fastener.
The pipe should have no effect on compression.