im trying to build a wrx that has around 320 whp. ive seen that both the PE 1818 and the 1820 turbos are capable of reaching that horsepower level. my question is, which should i buy? the 1818 that has less lag but from what im getting from the sales ad, 320 whp is almost its max. or go for the 1820 which has more lag but can reach 320 whp more easily?