You keep mentioning anti roll bars, as in plural. I can’t imagine the front anti roll bar on a Cosworth missing, as it is needed to keep the keep the front suspension together. If it would be missing I’d expect the whole front suspension collapses the first time you brake a bit hard. The rear anti roll bar can be missing without huge impact. But if that was missing the car wouldn’t be oversteering at any opportunity, it would actually be understeering. Or are you running something non-standard like compression struts and a front mounted anti roll bar on the front?