Underdrive Pulleys

Lookin' to do a first round of hp boosting mods. Underdrive pulleys have been advertised for 10-15 hp increase at the rear wheels. My concern is that the reduced drive on the water pump would make me more susceptible to overheating. Any thoughts or experiences with underdrive pulleys? Thanks.

They work great, no issues yet. Ive had them on for about a year, I race, etc. No prob.

This is something that I'll do after I get some SFC's and an STB. Probably won't get the advertised hp gains, those are under optimal settings, but they can't hurt, that's for sure...:D

I know several people that made no difference in HP or TQ from UD pulleys, but made 1 to 2 tenths faster at the track.