I didn't weld in a bung. Im using a tailpipe adapter. tested with and without and go same reading so mine seems to work fine with the adapter.

Looks like dist etc just arrived back home. So will get into it on Monday and advise the outcome. I have lots to check now with all your input. I also have a tiny fiber boroscope, so I can get into each cylinder and see if anything what`s happening in there too. Im worried now about the detonation issues. But I think it`ll be ok as I only moshed it a few times.