My gelding used to run in a hackamore because he is so light mouthed.  He got to where he was just kinda floating around the barrels. I swapped him to a bit that had shanks but a Mullen mouth with a copper roller. I forgot his bit yesterday when we went to the arena for a practice run. I ran him in one of my others. It was just a simple O ring with a large twisted wire. OMG his turns were AWESOME but he’s sooo light mouthed that I could tell I was putting pressure on him, slowing him down. I’m not heavy handed but I’m not the lightest either. What’s something I can try that will keep the snappy turns but have little to no whoa. He doesn’t need any help stoping. I sprint him in a halter and he stops just fine. 

Personally, if it were my horse, I'd do some drills or slow work to remedy this issue before trying a new bit. Have you tried asking your horse to immediately counter arc a few strides coming out of each barrel during slow work? That and sometimes a few sessions of rollbacks on the fence usually get my mare snappy in the turns again. 

A bit is not going to help your horse become snappy IMO. You need to do some drills to help that.

I didn’t know there was any or what they were. I’ll try the one from above. What else is there? 

There are lots of great videos on the youtube

https://www.youtube.com/results?search_query=how+to+make+snappy+turns+barrel+racing

Yes, a bit doesn't make a horse run. 

Your body language is what does that.  Try some Lance Graves videos too.  You can't just be a passenger, you need to help your horse. 

There a some videos on trainingbarrelhorses.com