I was driving without the thermostat for a while and the engine gained power. It picked up faster and would fly after 5000 rpm.I just put it back on yesterday and the differnce is obvius. I don't know why but the only thing I can think of is that it puts less pressure on the water pump which then puts less pressure on the pulley. (like the AC thing). What do you think?

Its constitanly flowing engine coolant through the whole system, so its keeping the engine alot cooler, which causes it to able to produce a little more power. When you have your thermo in, you car has to heat up for it to let the engine coolant run through, with it out its consitantly running through, even when cold.

You right, but that is only till the engine worms up. Once its wormed up (176 degrees) the thermostat is open doing the smae job as if it wasn't there. Wtihou it the water flows easier and faster while the engine is at the same temperature as if the thermostat was in. The thing is, I don't know how much good it does to the engine. It takes it a good ten-fifteen minutes to worm up witout the thermo.

Ya, I was asking my manager where I work about it(he is like a engine god) He was saying on newer model cars its could affect because they are made to run at peak perfromance at certain tempatures and when u take the thermo out, it cannot reach them temps. and therefore you lose some performance, AND it can possibley be bad for our cars, b/c when the engine does heat up and coolant starts flowing, it doesnt stay in the radiator long enough for it to cool down, which when then can cause overheating and loss of performance.