The beginning of a trend? Tipping point reached?

If I don't see signs that it's working, it's not working. I was seeing signs that something was working, and now,....not so much. Like a certain combination of adjustments was making my racecar work pretty good, except that I need a little better performance. How do I decide which part of the combination to change? I wish that I could afford to hire someone who knows more than I do. I wonder if Robeto knows?