Suspension is helpful. I’m not really making “downforce” as much as I’m just reducing lift. The spring rate on my car shouldn’t need to change to accommodate the splitter and wing I built. The goal of this stuff was to reduce lift over 100mph and make the car more predictable and smoother in fast sweepers and under heavy braking at the end of long straights. It’s working but I’m still tuning the angles to reduce drag and regain top end.
If you’re roll racing you probably don’t need aero stuff since it’s mostly straight line quick pulls. It’ll add unnecessary drag. A LSD, bracing, big front tires, stronger axles and probably frequent hub changes would benefit you more, if you’re pushing 500whp.
I‘d probably buy a different car to straight line race but that doesn’t mean everyone else should too. A lot of guys seem to drag their Fiestas and have good success. I might not get it, but many people I know have no clue why I choose to track a Fiesta lol. Whatever... Making a slow car faster is part of the fun. It’s what we do isn’t it?! No one here bought a Fiesta for its numbers. That’s what Hellcats, Mustangs and Honda Accords are for. I doubt I’ll set records with my car but it’s cool as f^#k and building it is fun. I rarely see other Fiesta STs and that’s pretty cool too. Good luck hitting 500whp man, I’m rooting for you. It’ll be a bad ass car for sure.