I thought I might have replied to this thread already but I hadn't.
No boosts are needed for my Diezels. I've used a CAL Mk.4:23 Pro as a clean boost, but that's it - and this was only for volume. As per Steve's comment above, there's a built in master/loop boost that's easily used for the same purpose.
I like stomps. Fact is I love 'em. Lil' boxes of goodness. But I find with every Diezel I've owned and used, there's simply no need for dirt, overdrive or boosting. In fact, less is more with Diezels, and that goes for the myriad of possible effects out there, IMHO.
Uncle Mo