nick from fast ford was running 230 odd bhp in his s2 when his engine let go (got to say took him a long time tho) upon inspection he said it looked as if a rod bolt was to blame. i think they are fitted as pice of mined and only realy needed in high reving engines..........its all a gess tho alto im building a frst cvh at the minit and i will be fitting arp's just to be sure