Gen 2 cycling issues sometimes at stop

Hey guys,

Im new here I just recently got a new prius gen 2 2008 103k miles and its been great so far. Ive been having issues with the prius trying to cycle to electric at a stop sometimes. it feels like it goes mid way but doesn't make it through and it ends up vibrating then my car starts to smell like gas.

I think this has been caused by premium gas in the car. I think it was happening beforehand but I am not sure.

Did I mess up my prius? I looked around and that it could be an exhaust leak but where would I look for that? I like to try to do some mechanic work myself but if not then ill have to resort to a dealer or a local mechanic