parallelizing HC on PBS with Queue

Hi!!!
I'm attempting to use Queue on PBSPro HPC cluster. I have tested the functionality of a custom scala script for Haplotype Caller and it is runnable. However, following the discussion on GATK forum, I should need a job scheduler to dispatch queue output on several nodes..could you give me some advice or examples of the type of scheduler I need in a PBSpro system?
I tried to run Queue on a single node and it seems working faster..the question is: when I run Queue on a single node I actually 'multithreading' HC or I'm wrong?
Thanks a lot
Best Regards
Marco