I did determine that the control was using the default IE webbrowser. Wireshark output is as follows:
0090 73 65 72 2d 41 67 65 6e 74 3a 20 4d 69 63 72 6f ser-Agent: Micro
00a0 73 6f 66 74 2d 57 69 6e 64 6f 77 73 2f 36 2e 31 soft-Windows/6.1
Also, using the following code in my app
System.Windows.Forms.WebBrowser wb = new WebBrowser();
wb.Url = new Uri("about:blank");
string userAgent = wb.DocumentText.Substring(js.Length);
produces the following output:
"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; MDDC)"
Previously, I had briefly checked both browsers (Firefox and IE) for any issues. Neither exhibited any slowness issues during my very brief test independent of using my control. So, I focused my attention on potential Webbrowser control issues. I revisited IE after wireshark etc. gave me the impression that it was the default browser used by the control and realized that initially it is very fast as in one second refresh rates but it eventually slows down to about 5 second refresh rates. The five second refresh rate become consistent with IE after a few minutes.
So, now I have to override the default bahavior of the control to use Firefox if it is installed. Otherwise, I'm stuck with IE.
Unfortunately, I developed "tunnel vision" on this issue and incorrectly made the assumption that the control was the source of the problem.
Thanx guys. I really appreciate the help getting me back on the right track!