Without MHL connected my test shows 4Mbps and goes through the test consistently with no hitches and all, my videos/streams play perfectly. As soon as I connect MHL the speed test goes to 1.5 at best and also stops and starts during the test. My videos/streams take longer to start and often freeze. I even tried starting a test, it was running fine at 4Mbps as usual, then connecting MHL during the test and as soon as that "HDMI connected" notification appears the test drops down towards 1Mbps and stalls repeatedly. Its really quite bizarre.
I'm using an official HDMI adapter, my wireless security is set to 2.4Ghz B/G and I've tried numerous channels all with no change. I have security on WEP, because at first I thought WPA2 was causing the problem, but I also tried no security again with no change. No doubt its not a WIFI signal problem though as WIFI Analyzer has since shown me.
My current ROM is Optimus 4.0 XWLSW. I decided on this because unlike a lot of other ROMs it supports MHL TV out. So if anyone has any suggestions on another good MHL compatible ROM to try please let me know. Any other suggestions welcome, cheers.