Cossie did get something wrong...the inlet plenum...hence the drasticaly modded rs500 item that replaced it for proper power capabilities. Ive got a 14mm spacer fitted on mine...fits straight on, the injector rail fits on by reverse bolting it up at the original points along with a 8mm(ish) spacer fitted between rail bracket and plenum cover. tbh tho their main restriction is in the elbow...im gonna look at a few swedish styles plenums later this year to over come this.