Wireshark won't help you if you have to debug HTTPS requests (unless you can get the encryption keys for both endpoints - see the Wireshark site for details). Firebug and Tamper Data are getting close, but for thorough analysis, I sometimes like to save a recorded session. I'd recommend giving the OWASP Zed Attack Proxy (the successor of Parosproxy, which is no longer actively developed) a try. It is a Java application serving as a http(s) proxy; it provides quite a lot of features and proved to be very helpful to me in the past.
ZAP offers an easy autoconfiguration of Firefox. Bear in mind to do that on a separate (meaning: not for other browsing activities) Firefox profile: In order to intercept https, ZAP will install a new SSL certificate.