I've tried in this order -
1.) EVOMs
2.) Dbilas
3.) ITG Maxogen
The EVOMs was by far the loudest and the Dbilas by far the quietest, obviously leaving the ITG in the middle.
I'd even refine my comments to say the EVOMS is intrusive all of the time i.e. normal driving and pushing on, the Dbilas only slightly noticable under normal driving conditions and idle and the ITG not at all noticble on idle and only noitcable under mid / heavy acclearation - but still not as loud as the EVOMS which sounded like someone had chopped a hole in my bulkhead somewhere.
All the above on mapped cars.
PS the Dbilas is going up for sale soon if anyone is interested PM me.