Server bottleneck Issue preventing opening Concurrent Http requests with proxies

Hello, I have a server where I am experiencing some trouble opening concurrent http requests using proxies . For the purpose of testing I used apachebench util , and the same request which takes 10seconds in all other servers I tried takes forever in this particular server when using proxies (works well without) . I am considering this may be a egress filtering issue at the network level but if you are an experienced sysadmin maybe there is something else which may be preventing my server from running proxy http requests concurrently . Need remote assistance with this issue and will pay hourly . If you believe there is something which can be done to address this issue at the server level please message . Thank you