OP, perhaps you should show us some of your actual code that you've been profiling. We may be able to help you out with optimizations on the original code. I have a feeling that getting more eyes on the original code would help you more than asking for ideas about turning statements into expressions.
Post some side-by-side blocks of C# and disassembly (x86/64 or RISC, whichever you're targeting, not the IL) and demonstrate the problems you're seeing. And I mean full functions or algorithms, not just individual statements like your first post has. Those are out of context and are not useful to optimization discussions.