Plugin is getting slower

php language itself is infamous for inconsistent performance for long dreaded tasks such as ingesting a 22,000 line csv row. you could try finding memory leaks if you have any knowledge of debugging php. I built this script in an object oriented pattern to reduce the likelihood of memory leaks but even the best written script will still have issues as php itself is known for memory management issues when running exhaustively. Over time I can tweak things here and there that may make the script a little faster but as of now I suggest you cut that csv file into 11 pieces if you would like the script to ingest 11 csv files in 11 hours at 2000 lines per file. I hope this helps.