I have been running a crossover w/thermostat and bypass hose for about 6 yrs. Like Eddie said, you need to drill a couple of holes around the edge of the stat to make it flow better. I run 7psi at idle and about 25psi after planned out. My temps are actually more stable than before and plenty of flow out of the tips. As for the HP gain? Don't look to see any extra on the speedo.