RE: Traxxas Slash Stutter....
I had to laugh at the thought of merely using lipos as the reason for the stuttering....if anything, it should help
If I had to guess without any information besides "stuttering" and "stock" I'd say your motor is giving out. Try a different one. The Titan 12T can last for months (for some people, rarely) or it can last for 2 weeks (happened twice to me, 2 different modes of failure).
Other than a bad motor (most probable) I'd say messed up radio settings/equipment.
If it is the new XL-5, it's actually fully lipo-ready anyway...