Launching VS Profiler boosts Application Performance x20?

Running with the debugger disables jit optimizations. If you run the exe normally jit optimizations will be enabled. Attaching a debugger to such a running application allows you to debug it with enabled optimizations.

Release-Build vs Debug-Build has two consequences:

1. A conditional compiler symbol is (un)defined
2. It enables/disables optimizations in the C# => IL compilation.