PerformancePlus (PP+) is an unofficial osu!Standard ranking system meant to better represent player skill. Drezi started the project on July 31st 2016 and is it's main developer, DT joined in as a helper/general advisor in the developing stage, and Syrin developed and hosts the website. The project started as a response to the lack of alternatives to PPv2.
By the limits imposed on us by the official osu!API, we are only able to check the top 100 scores on each map. You are free, however, to add your own scores by using the Add score function on your profile page. Since one is able to submit a seperate score for each given mod combination, Add score takes the highest (total) pp-giving score, in accordance to PP+ calculations. This is also useful to overwrite a possible higher score-giving HD/HDHR score with a higher pp-giving submitted HR/DT score on the same map that didn't surpass the HD score on the leaderboards!
As the algorithm will never be perfect, there will always be outliers that might look bad, however one's own perception may skew their expectations towards what they are used to. Accuracy and length scaling are now different, so PP+ behaves differently at lower and higher accs depending on the map, with respect to PPv2. Your own intuition from PPv2 on how a low accuracy score might imply something about the same score with high accuracy, or the relation between nomod and HR, might not transfer quite the same under PP+ conditions.
Before submitting a complaint, please crosscheck the score with higher accuracy scores, different mods, and the subskill values of the score with other maps. If you still think it is unfairly gaining/losing pp, you are welcome and encouraged to let us know what you found!
While effort has been made to keep everyone about at the same level as PPv2, PP+ totals are made from PPv2 totals plus the combination of the three main skills, so everyone generally gains some pp. But pp is just a number, what matters most is their rank!
Thank you for asking! The server is not very powerful, so donations would help us/help Syrin (make your pick) pay for the server.
Support PerformancePlusPlay more.