I wasn't suggesting that a compression gauge will help you tune an individual engine, per se, but it will help show you how worn your internals are, and in the long run it can help you try to coax more life out of your engines by running them a little differently. In addition, it can help you determine the relative effect of adding or removing head shims. In my view, more info is better than less, and compression is certainly useful info on any internal combustion engine. Besides, they are petty cheap, its not like I'm telling the guy to buy a dyno or anything