I know nothing about fuel additives, but I have been around plenty of cars that make me cry (and not crying from envy, those are different).

My dad had Z car that would get exhaust fumes inside the car if the tail pipe wasn't right. It would be awful after a few laps and that car was just running pump gas.

I remember trying to tune a carbed car that was running race fuel and was so over fueled that even w/ the car pushed outside the shop it was unbearable.

So it may not be so much of an additive as it is a poorly running car. SRF's are carbed (aren't they?), were the other offending cars FI or carbed?