Weapon draw REDUCTION. There you have your heat - Meaning you need more Pips to Weapons to keep em cool if its possible at all.
More Pips in Weaps -> faster Weapon cooling in general.
Cheers!
Did this upgrade on 2 heavy pulse lasers and got little to no heat increase. The Weapon draw is REDUCED in this mod, not increased so it's a positive effect and not a source of heat increase.