4x4min w/ 2min RI
Either extend to 4x8 w/ 2min RI or do more 4min in a row. IE 5x4, 6x4.
Also, miracle intervals since it sounds like you may have less punch than others in your race category.
Not sure what weight you are but that may be a sneaky source of improvement too...accelerating excess of mass 1000 times a race takes it out of you.