UPX makes program "faster"?

Is it normal that after packing my injector with UPX it greatly improved in execution time?

I added an execution timer to my manual map injector for testing purpose and after packing it, it went from taking about ~900 microseconds to inject my dll into a process to about ~300 microseconds, will this affect pretty much any program or is it a rare occasion (I really don't have time or the nerves to test it further)