Car runs the same

You should start with looking at the incrementals on the time slip of the 5.80 run, then compare to your current runs so you can see where the issues are. For example, if the 60' time is off but the MPH is the same, then you may have a tire issue or suspension setting issue....If you are down on MPH then you have a motor tuning issue, etc.

To be honest, if everything is working as it should, going from a high 5.9x to 5.7x takes a LOT more power...you may just have to run another race.