As every time.

1st safe the original file (wop_fw190D.cab).
Remove the cab from the -Gauge- folder.
Create a new folder -wop_fw190D-.
Unzip the whole -wop_fw190D.cab- and get all files into the new folder -wop_fw190D-.
Now you can start with changing bmp and xml files, if you like.
This is the original <Help ID>/<Tooltip ID> from -Airspeed Indicator.xml-
<Mouse>
<Help ID="HELPID_GAUGE_AIRSPEED"/>
<Tooltip ID="TOOLTIPTEXT_AIRSPEED_KNOTS" MetricID="TOOLTIPTEXT_AIRSPEED_KILOS"/>
</Mouse>
You have to replace this part of the XML listing with the modified one
<Mouse>
<Area Right="114">
<Tooltip>IAS = %((A:Airspeed indicated,kilometer per hour))%!1.0f! km/h</Tooltip>
</Area>
<Area Left="115">
<Tooltip>TAS = %((A:Airspeed true,kilometer per hour))%!1.0f! km/h</Tooltip>
</Area>
</Mouse>
You will get with this modification two different speed indications.
When the pointer is on the left side of the airspeed indicator, you will see
IAS = Indicated Air Speed = the same what the instrument shows
When the pointer is on the right side of the airspeed indicator, you will see
TAS = True Air Speed
For the fellows which like to see the speed in knots, replace -kilometer per hour- and -km/h- with knots.
As next - S A F E - the new file under the old name -Airspeed Indicator.xml-
al tom