Do you hear loud rattle inside car? it does sound a bit like overpipe or something hitting on chassis at initial startup.
you can quieten/tame down the start in the tune
Set Post timing ignition from -15 to about -6, see picture below
You will need to disable CEL code P050B (post timing ignition timing performance) else on USA roms you will throw a CEL
Set MAF correction after start in gear and neutral tables as per picture below
Set any numbers in idle control tables set any values over 1400 to 1400 ie if its 1800 set to 1400
Then startup will be quiet.
