No, I read somewhere that adding a lower thermostat will actually hurt your performance because your engine is design to operate best at it's normal operating temperature. Increasing or decreasing the N.O.T. will just lead to problems and decreased performance... Don't do it...
By the way, I think I read it on the MAC website.
www.macperformance.com it's either under FAQ's or the info about adding headers section...
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2000 GT Conv. 5speed
Triple Black
Current Mods: K&N, Mobile 1
ET: 14.6@99.8 (Bogged)
Upcoming Mods: BBK Longtubes, BBK H-pipe w/cats, MagnaFlow Cat-Back, and much much more