Unless you pull the engine out and put it on a dyno, it won't tell you much. A chassis dyno will tell you what is getting to the wheels which is anywhere from 10-25% less than at the flywheel.
Then factor in production tolerances, age, worn components, and the fact that every dyno is vastly different, your numbers won't mean a thing. Not to mention, GM's advertised hp rating is only a ballpark guess, not measured on a dyno. Even if it were measured at exactly 130 on a dyno at GM, that means nothing on a dyno in MD.
One dyno might tell you 100 hp, then the one across the street will tell you 120hp on the same day. The only good a dyno will do for you is if you had a baseline reading from prior to when you discovered it was sluggish, and then go back to the same exact dyno to retest and use environmental conversion factors. That would get you within a few percent.
If you want to dyno it just for giggles, go for it, but any dyno session you pay for now will be a waste of money, especially because the only thing it would do is confirm; "yup, its sluggish." It won't tell you why.
Your butt is the best dyno you have.
