160 vs 180 Thermostat

I just wondering what you guys have and what is your opinion about thermostat
First I had 192(stock) than I change to 180T , than after a few months I change to 160T and today I change again to 180T,
I know that with 160 thetmostat engine can colder ,but there is one problem , one my friend(guy who work on Mustangs 20 years and who have 94 347 Mustang with blower) tell me when I have 160T computer think engine is cold and dupm more fuel and engine could run rich,
So what you guys say which one thermostat better for lightly moded N/A Mustang like mine

Here is two pics of gauge how looks like with 160T and 180T and high speed fan on

<img src="http://forums.stangnet.com/attachment.php?attachmentid=18449&stc=1">
<img src="http://forums.stangnet.com/attachment.php?attachmentid=18450&stc=1">

One thing I forget to say , I run with high speed fan on 165(with 160T) or 185(with 180T) but when I turn of high speed fan temp is 212F doesn't metter whish one I use thermostat 160/180


here is one pics without high speed fan off

<img src="http://forums.stangnet.com/attachment.php?attachmentid=18455&stc=1">