New ElasticSearch Node.js client "@elastic/elasticsearch" slower than legacy ElasticSearch Node.js client "elasticsearch" in searches

Hi folk,
We are using ES version 7.9.0, the application that uses ES is on the NodeJS platform. We have currently replaced the legacy ES client library ("Elasticsearch": "16.7.2"), with the new ES client library "@elastic/Elasticsearch": "7.9.0". During the change some parts of the code have been modified as indicated by the documentation. The tests did not reveal any particular code problems or errors, such as connection errors.

Instead in doing the performance tests a slowdown in searches emerged, there are no errors but I repeat only slowdown in searches compared to the old client. The average search times under load are as follows:
legacy client average time 630 ms
new client ES average time 860 ms

Has anyone encountered this problem? in the transition from the old to the new ES client? do you still have any suggestions or opinions on the matter?

Thanks in advance.