IM not a mechanic. all i know is what overkill told me when i got my first tune(just cai and u-bend delete & 91 octane tune dont know if that makes a difference) that when i get a hv3 to get a retune, that he would get more power.
so i did that just yesterday, he drove it for a bit, pulled over, said i was running lean so he added fuel and some timing, took a run, did it again,added mroe fuel & timing, took a run, did it again. then he changed some part throttle fuel trims and i was done, and i can honestly say pulls alot better now then it did before the retune.

Ask overkill as i dont know im just going by what he did/said.