HTTP request C# .NET?

See the difference the headers. There is nothing more to say.

Then only last option is that proxy caches and, therefore, no lag. If your proxy is transparent, in fact in direct connection, or through it, there is no difference, there is only a cache.

If you are compiling (in the Studio or not), the lag may be due to fierwall, because it establishes that the new program was breaking on the Internet.
\r
Through the proxy everything is OK, because the proxy program is still the same, and the rules the firewall uses the same as before.

Please don't put such high hopes on fiddler, it is sometimes very randomly. I once after a normal completion of a Fiddler stopped working my program, although Campiglio and re-launched under the Studio without it. All was resolved only on the next start Fiedler.
\r
And drop by timeout normally. Anyway, these eksepsi need to catch and send the request again. Just don't do an infinite loop, you still need to limit the number of connection attempts.

I had a similar problem, after 2 days of analyses was that violated a certain sequence of queries, i.e., before performing a desired Request'was necessary to run the empty POST on a certain page.

Compiler in the release.
Create a rule for Firewall.
Nothing helped.
All all works well with ukljucenim a Fiddler, and still timeoutid without him.
\r
Proxy does not cache, it is essentially a sniffer, it can cache anything.
\r
PS
Checked on 3 computers (work, home, the remote server behind a cordon)
\r
Maybe the problem in the HttpWebRequest?

Definitely not.
This is excluded by the facts of checks in 3 different places.
And never notice the posts.