Noted that removing comments provided "noticeable improvement" but the other ways you mention in terms of tightening your code are UNLIKELY to provide similar gains.

Before concerning yourself with whitespace and even $exceptionally-extraordinarily-long-and-verbose-nomenclature-for-each-and-every-possible-variable, try profiling your code. Some good reading? The Rules of Optimization Club and the other threads you'll find here with a Super Search for "nytprof" or "profile."