Does the custom warpig set have an alnico neck? It's very hard to get truly good cleans from a super hot ceramic pickup (although the advantage is it doesn't sound weedy when split, which could be another option), so you may want to have a very hot bridge and then switch to the neck for cleans
HOWEVER, if your wanting to play Metallica then chances are you never play truly clean anyway, a little chorus and delay will take off those brittle edges nicely.