What do they need to be? as in regs wise would a decent motorbike helmet be up to the job? looking at doing a few events next year (scoobyshootout for one) and don't want to buy one and find its not suitable.
personaly i'd only use vpower or tesco 99 in a turbo'd car, especialy if its not standard. and also bear in mind if yours has been mapped you need to use the same fuel or higher ron than it was mapped on