Cel

I have read through most of these posts, and it seems my prob. is unique. I seem to have lost a bit of power, but of more concern is when under full throttle, the car will stutter, as if it is misfiring, with no late or off detonation, and the check engine light will flash for 20-50 seconds and then turn off. At first i thought it was a problem with the coolant, (where the engine would run on half its cylinders, using other half as air pumps, but my coolant is fine, and my resevoir is full, and my pump is working fine.
Maybe fuel filter?
Also (this one seems to be more common) it has been overheating sporadically, and is fine after key is out for a minute or so and the code clears. My question is; since the criminal is most likely my thermostat, does anyone know if the 2001 LS 3.9 is located on the bottom of the engine (from other thread) as the 2000, or at the upper radiator hose(industry std.)